I totally agree with AHBD, based not only on my own, personal Bearded Dragon experience of over 15 years, but also based on every single scholarly journal article and book that I've read on the subject, Bearded Dragons WILL NOT brumate at all until they are at least around 7-8 months old, and even that is extremely rare, usually they don't even attempt a brumation until they are well over a year old, and something that people need to keep in mind is that a good percentage of Bearded Dragons kept in captivity NEVER BRUMATE, they don't even go into a partial-brumation at any point during their lives because they don't have to, and because their artificial environments in captivity keep them from sensing the need to brumate. I had my first dragon from 2 months old until he died at just shy of 13 years old, and he never once showed any signs of wanting to brumate. So a lot of very experienced Bearded Dragon owners have no experience at all with brumation. And in my experience, a lot of the time (especially if we're talking very young dragons) when a dragon is constantly going into brumations there is often a husbandry issue related to temps and/or the lighting that is causing the problem.
We also need to keep in mind that Bearded Dragon do over 80% of their growth and development during their first year of life, so this is exactly the reason why most young Bearded Dragons even in the wild never go into any type of brumation until they are at least a year old, because it would be detrimental to their health and development. They need to be eating tons of insect/animal protein every single day and getting adequate sunlight in order to grow properly. So this is the main reason that young dragons don't brumate.
And a real issue on all Bearded Dragon forums, in my own personal experience, is that "Brumation" is used as a catch-all answer any time a dragon loses their appetite and/or becomes lethargic, when in reality (as in this particular situation) the reason they are losing their appetites and/or becoming lethargic is due to a husbandry issue regarding their lighting or temps. And whenever someone responds with the answer "he's probably going into brumation" without even asking any husbandry questions, or for that matter any questions about the rest of the dragon's behavior, this is how severe nutritional deficiencies develop, the most common one obviously being a Calcium Deficiency and the resulting MBD due to inadequate UVB and UVA lighting, which is exactly what is most likely going on here. So it's always a good idea to hold-off on the "brumation-excuse", as I like to call it, until you've gone over all of the owner's husbandry and diet/supplementation schedules and ruled-out these as the cause.
If your Reptisun 10.0 UVB tube is the weaker T8 strength, then this is definitely part of the problem, possibly the entire problem. The first symptom of inadequate UVB/UVA lighting is a sudden loss of appetite, followed or accompanied by sudden lethargy. There's nothing wrong with using a Reptisun 10.0 T8 UVB tube for a Bearded Dragon, it's one of the best T8 UVB tubes for Dragons available (along with the Arcadia 10% T8 UVB tube), but you have to know it's limitations and the rules of using a T8 UVB tube versus using a much stronger T5 UVB tube.
The Reptisun 10.0 T8 UVB tube (as do all T8 UVB tubes) must not be obstructed by ANYTHING, including a mesh tank lid or any type of clear, plastic cover on the bottom of the tube fixture (some tube fixtures have a clear plastic "safety cover" on them that cover's the UVb tube, and no strength of
UVB light can at all penetrate clear plastic or glass, so this blocks 100% of the
UVB light emitted by the tube), as most of the mesh lids block around 40% of the
UVB light emitted by the tube, and T8 UVb tubes are far too weak to still emit adequate
UVB light to your dragon on the other side of the mesh. In addition, your tank is quite tall unfortunately, which is always a problem with Beardies and a T8 UVB tube, because the T8 UVB tube must be within 6" of the dragon's basking spot/platform to emit adequate
UVB light to the dragon. So hopefully once you poke holes in that mesh lid and get that fixture strapped to the underside of the mesh lid, this will put the now-unobstructed UVB tube within at least 6" of your dragon's basking platform. Also, all T8 UVB tubes have to be replaced once every 6 months at a maximum, as they have a very fast UVB decay rate and stop emitting most all
UVb light around 6 months old when tested on a Solarmeter.
In contrast, if you were to buy a T5 strength UVB tube, it's going to be strong enough to be able to sit on top of the mesh lid and still emit adequate UVB and UVA light to your dragon (which is always a much better choice for a Bearded Dragon, but specifically if you have a tank that is taller than it is wide/long), the T5 strength UVB tubes (as long as it is at least a 10% UVB tube, or at least a 10.0 UVB T5 UVB tube and not a 5% or 5.0 or less UVB tube). The real advantage to a T5 strength UVB tube that is at least a 10% or 10.0 UVB tube when you have a tall tank is that the 10.0 T5 UVB tube only needs to be within about 11" of your dragon's basking spot/platform to emit adequate UVB and UVA light to your dragon (instead of having to be within 6" of the basking platform as the T8 UVB tubes must be, which is sometimes difficult to accomplish with a tall tank). Also, there is a financial advantage to the 10.0 T5 UVB tubes, as they only need to be replaced once every 10-12 months because they have a slower UVB decay rate than the T8 tubes. So you save money that way, and also because if you purchase a Reptisun 10.0 or an Arcadia 12% T5 UVB tube online, they are almost always cheaper than the T8 tubes are, the only extra cost you'll incur at the purchase of your first T5 UVB tube is also having to buy a tube fixture that is not only the same length as the T5 UVB tube you are buying, but you must also purchase a tube fixture that is rated for a much stronger T5 UVB tube, as most T8 tube fixtures are only rated for between 15 and 17 watts, and the weakest T5 UVb tube I know of is 24 watts.
Also, I don't know how you usually have your UVB tube and your bright-white colored Basking Bulb set up over the tank (I know the current photo is the temporary set-up), but a lot of people don't realize that both the UVB tube and the Basking Bulb must be over the Hot Side of the tank and right alongside each other (not end-to-end but rather right alongside each other), in a way that they are both "sharing" the entire top of the Hot Side of the tank/enclosure. I see a lot of people who put the Basking Bulb obviously over the Hot Side of the tank, but then they have the UVB tube/light either centered in the middle of the tank or over the Cool Side, and this is totally counterproductive and can result is just as many health issues as having an inadequate
UVb light or an obstructed T8 UVB tube does.
Your main goal when setting-up the UVB tube and the bright-white colored Basking Bulb over your dragon's tank is to replicate natural sunlight as closely as possible for your dragon over the Hot Side of the tank, so that your dragon not only gets BOTH LIGHTS at the same time while basking on his basking spot/platform, but also that he is doing this basking under both lights in a Basking Spot Surface Temperature that is between 105-110 degrees F for a baby or juvenile, and between 100-105 degrees F for a dragon that is over a year old. So if you have the UVB tube centered in the middle of the tank or over the Cool Side of the tank and the obviously must have the Basking Bulb over the Hot Side of the tank, then he's not absorbing any of his UVB or UVA light in the proper temperatures that enable him to digest his food. So you want both the UVB tube and the Basking Bulb over the Hot Side of the tank, both right alongside each other so that both lights are "sharing" the top of the Hot Side of the tank, and then you must position his basking spot/platform so that it's not only within the Hot Side of the tank, but also so that it's directly underneath both of the lights, so that he's getting both lights at the same time while laying on his basking spot/platform and within/on the correct Basking Spot Surface Temperature range. Also, make sure that both his lights are on for at least 13-14 hours every single day.
Some people also need to add a second, much lower wattage, bright white colored Basking Bulb over the Cold Side of the tank in order to get the Cold Side Ambient (air) Temperature between 75-80 degrees F. A lot of people try to get all 3 temperature zones within the correct ranges with the use of only the main, higher-wattage Basking Bulb, but this is sometimes impossible and will drive you insane if you try to do it, lol, so I tell people to make this easy on themselves and only use the main, higher-wattage Basking Bulb that is over the Hot Side of the tank for getting #1) the Basking Spot Surface Temperature and then #2) the Hot Side Ambient (air) Temperature correct, do not even measure the Cool Side Ambient (air) Temperature UNTIL you get the Basking Spot Surface Temperature and the Hot Side Ambient (air) Temperature within the correct ranges. THEN measure the Cool Side Ambient (air) Temperature, and if it's not at least in the low 70's then simply add a clamp-lamp or dome lamp over the Cool Side of the tank with a low-wattage, bright-white Basking Bulb (or Halogen Indoor Flood Bulb), usually a bulb around 30-40 watts will do the trick.