He doesn't look good. First of all, your temperatures are way off, and I'm assuming that you are using only a stick-on thermometer since you only listed 2 temperature ranges. You need to get a Digital Probe Thermometer, which has a Probe you can sit right on his basking spot where he lays, let it sit there for at least 20-30 minutes, and then read the temperature. This is the Basking Spot Temperature, you cannot measure his Basking Spot Temperature with a stick-on thermometer, what you're measuring is the Hot Side Ambient and Cool Side Ambient temperatures, or Air Temperatures.
Here's the thing, the stick-on thermometers are very inaccurate, usually off by between 10-20 degrees when tested. And the actual Basking Spot Temperature, which should be right directly under both his UVB tube and his bright white basking bulb, is going to be considerably higher that the Hot Side Ambient (air) Temperature around it...So if your getting 90-100 degrees as a Hot Side Ambient Temperature with an inaccurate stick-on thermometer, my guess is that the Hot Side Ambient (air) Temperature is actually more like 110 and his Basking Spot Surface Temperature is in the lethal range, over 110. And the Cool Side Ambient you are getting is 85-90 degrees, which is probably closer to 100 degrees in reality, when it should only be 75-80 degrees absolute maximum.
So you're most likely cooking him!!!
A Digital Probe Thermometer costs $10 at any Petco or PetSmart, I suggest you go buy one ASAP, bring it home, and immediately start measuring all 3 temperature zones, starting with the Basking Spot Surface Temperature. Put the Probe on the wire right on his main Basking Spot/Platform (which again needs to be located within the Hot Side of his tank and directly under both his UVb tube and his bright white basking bulb so he is getting both at the same time while he basks). Allow the Probe to sit for 20-30 minutes and then read it. Then you need to measure the Hot Side Ambient Temperature, and you do this by taking the Probe and using the suction cup that comes with the Digital Thermometer. You attach the suction cup on the wire right below the Probe, then stick the suction cup to the glass on the Hot Side of the tank, about 2" from the floor. Again let it sit for 20-30 minutes, then read it. Then move the Probe to the opposite Cool Side of the tank and stick the suction cup to the glass on the Cool Side about 2" above the floor, wait 20-30 minutes, then read it.
My guess is that all 3 of your temperatures are far too hot and you're going to need to buy a lower wattage bright white Basking Bulb or just a regular Halogen Indoor Flood Bulb like you buy at Tractor Supply, Lowes, or Home Depot. I don't know what size tank you have, but typically a 40 gallon breeder tank only needs a 100 watt bulb, any smaller of a tank and you need to go down obviously. But I'd go out and buy the next wattage down from whatever you're using, and please be sure it's bright white only, no colored bulbs at all for Bearded Dragons, and no Coil/Spiral bulbs either.
BASKING SPOT SURFACE TEMPERATURE (Within the Hot Side of the Tank where he lays to bask): Should be between 105-110 for a baby or juvenile and between 100-105 for an adult. ***110 degrees is the absolute hottest temperature anywhere in the tank for a Bearded Dragon, anything over that is lethal.
HOT SIDE AMBIENT TEMPERATURE (Air temperature on the Hot Side of the tank, surrounding the Basking Spot/Platform): Between 88-93 degrees maximum.
COOL SIDE AMBIENT TEMPERATURE (Air temperature on the Cool Side of the tank): Between 75-80 degrees maximum.
***So you can see how hot your temps are, even without assuming that your stick-on thermometer is accurate, which it probably isn't.***
The second issue is most likely your
UVB light...Is your Reptisun 10.0
UVB light a long tube that is 18" or 24" long and in a matching length fixture, or is it just a regular compact or coil lightbulb?
If you are not using the 18" or 24" Reptisun 10.0 UVB tube (either a T8 or better a T5HO), then this is the other huge problem you have, as the Reptisun 10.0 compact/coil bulb and any other compact or coil UVB bulbs are completely inadequate for Bearded Dragons, they are at most 13 watts, some are less, and he's essentially getting no UVb or UVA light from it. And if it's being obstructed by a mesh lid, that is also blocking 40% of the already too weak of
UVB light. Also, if it's the coil/spiral version, they cause significant eye and neurological damage.
You need to buy a long UVB tube and matching length fixture, either an 18" or a 24", and it must either be a Reptisun 10.0 brand (not a 5.0) or an Arcadia brand. They come in two different strengths, a weaker T8 (you'll find this one in Petco and PetSmart for $37 just for the tube, and it's not worth it), or the more adequate and appropriate for Bearded Dragons the stronger T5 strength.
My suggestion is you go to Amazon.com and order a 22" Reptisun 10.0 T5HO UVB tube and then do the package deal for a 24" T5-rated tube fixture that includes a metal reflector with it. The 22" Reptisun 10.0 T5HO UVB tube costs only $23 on Amazon.com and you can do a package deal after selecting the tube for a 24" T5-rated fixture (yes, the 22" tube fits in a 24" fixture) for under $50 shipped for both, just be sure you choose the cheapest 24" fixture they offer that includes the Metal Reflector, this is not optional.
The difference between a T8 UVB tube and a much stronger T5 tube, besides that the T8 tubes are overpriced, especially in stores, is that the T8 tubes must be mounted underneath the mesh lids by using zip ties or something similar, they must be within 6" of the main basking spot, and they must be replaced every 6 months as that's the age they stop emitting any
UVb light. These are the same rules and your compact/coil
UVb bulb, they must be under the mesh lid, be within 6" of the basking spot/platform, and must be replaced once ever 6 months. The only difference is that the compact/coil UVB bulbs will cause horrible eye and neurological issues when within 6" of your dragon.
In contrast, the T5 strength UVB tubes can sit on top of the mesh lid as long as his Basking Spot/Platform is within at least 11" of the tube, and they only need to be replaced once every 109 months to a year. So you save money. Spend the $50 now on the T5HO tube and fixture, he'll perk up within a day or so of being under both an adequate UVB tube and in the correct temperatures (both lights need to be on for at least 13-14 hours every single day), and he'll start eating again pretty directly as well. Without an adequate UVB tube and correct temperatures he's going to get worse and worse.
I'd turn off the compact/coil
UVB bulb for now, go buy the Digital Probe Thermometer and get his temperature ranges correct, and order the T5HO UVb tube immediately. If you do happen to have the long Reptisun 10.0 UVB tube, it's probably an 18" T8 version, so if you have it on top of a mesh lid and not within at least 6" of him, then you need to poke holes in the mesh and use Zip Ties or Shoelaces to mount the T8 tube to the underside of the mesh lid, and get his basking spot within 6" of the unobstructed tube.