I see 2 major issues here that are causing his problems, and they are very serious issues. The main one is he's not getting much UVB or UVA light at all. The Reptisun 10.0 compact
UVB bulb is not at all adequate for a Bearded Dragon, as it's only 13 watts, and you also have it on top of a mesh lid, which is blocking 40% of the already far too weak
UVb bulb. So he's not getting much if any UVB or UVA light at all. That's the most serious problem you have. You need to get him a long, fluorescent UVB tube and a long tube fixture for it immediately, as he is probably already suffering from a Calcium Deficiency, and I'd hate to see the MBD start developing. Without strong, adequate UVB and UVA light for at least 13-14 hours every single day, he cannot absorb any of the calcium you are giving him at all, nor any other vitamins or minerals, and he's going to start developing a lot of serious healthy issues, such as MBD and Vitamin B1 Deficiency.
If you buy a weaker T8 strength UVb tube and fixture (17 watts), it will have to be mounted to the underside of the mesh lid by poking 4 holes in the mesh and then using long zip ties, wire, twine, etc. to strap the entire tube fixture to the underside of the mesh lid. The weaker T8 tubes must be within at least 6" of the basking spot/platform, must be unobstructed by anything like a mesh lid or plastic cover on the fixture, and must be replaced once every 6 months. The 2 T8 UVB tubes recommended for Beardies (must be at least a 10% UVB tube, or 10.0) are the 18" Reptisun 10.0 T8 UVB tube and the Arcadia 10.0 T8 UVB tube. Stay away from Zilla, All Living Things, and Reptile One T8 UVB tubes, as they all cause serious eye damage, blindness, and neurological issues.... It's better and will save you a lot of money if you instead purchase a much stronger T5 strength UVb tube and fixture, as they only need to be replaced once every 12 months. Also, the T5 UVB tubes are strong enough (24 watts at the weakest) that they can actually sit on top of the mesh lid as long as his basking spot/platform is within at least 11" of the T5 UVB tube. The 22" Reptisun 10.0 T5HO UVB tube ($24 on Amazon.com, and another $28 for a 24" T5 fixture) or the Arcadia 12% T5 UVb tube are the 2 most commonly used UVB lights by experienced Beardie owners.
The other major issue you have is how you have your lights set up on 2 different sides of the tank. You need to put both the
UVb light and the bright-white colored Basking Bulb over the Hot Side of the tank, so that they are right alongside each other and sharing the top of the Hot Side of the Tank. Then his main Basking Spot/Platform needs to be positioned within the Hot Side of the tank and directly under both lights, because he needs to be getting both lights at the same time while he's basking. Your main goal with a Bearded Dragon's lighting is to replicate natural sunlight as closely as you possibly can over the Hot Side of the his tank and over his Basking Spot/Platform located within the Hot Side of the tank.
The only light that you may want to have over the Cool Side of the tank is a second, much lower wattage, bright white Basking Bulb if the main Basking Bulb over the Hot Side of the tank does not keep the Cool Side Ambient (air) Temperature between 75-80 degrees. That's it. His
UVB light should not be over the Cool Side, nor should it be separate from the main Basking Bulb.
So since he's not been getting much UVb or UVA light at all, he's not properly digesting his food and not absorbing much calcium or other nutrition from his food or supplements at all. The Reptisun 10.0 compact
UVB bulb is unfortunately commonly sold to new Bearded Dragon owners, and unfortunately if the owner doesn't find out that ti's a totally inadequate
UVb bulb for a Dragon, they end up starting to exhibit the first symptoms of a Calcium Deficiency and MBD. Hopefully this won't progress with him if you get him an adequate UVb tube and fixture ASAP, and I can't stress this change that needs to made enough to you, as having an inadequate
UVb light and having the
UVB light/tube set up incorrectly or obstructed when it's a weaker T8 tube are the most common causes of health issues in dragons...