Your beardie has MBD, your UVB is probably not sufficient, some brands don't emit nearly enough UVB for a beardie, maybe for some "jungle" animals they are good but most are not good for beardies.
Best UVB would be ReptiSun 10.0 UVB tube/fluorescent (Arcadia 12.0 if you're in AUS) (DO NOT buy compact/coil bulbs, they are harmful to beardies, they can lead to eye problems + they don't emit enough of those much needed UVB rays), you don't want anything between the tube and your beardies basking spot (no mesh or plastic that comes with some reptile fixtures), your beardie MUST be able to get within 6 inches of UVB.
Your beardie should also get his Calcium with D3 powder supplement on one of the daily feedings/five times per week, other two days in week when he is not getting his Calcium with D3 you should give him MultiVitamin supplement.
Good calcium with D3 and good UVB tube (ReptiSUN 10.0 UVB) are paramount for beardie with MBD.
I really hope he'll pull trough for you, good luck!
If you have any questions at all please don't hesitate to ask, you can even send me a PM if it's easier for you.