Is he kept on any type of particle substrate? Sand, gravel, rocks, eco earth, jungle mix, calci sand, crushed walnuts ect?
What type of MVB do you use, wattage and brand and how its positioned. If you can please post pictures of the entire setup, lights, enclosure everything so we can see what living conditions are.
Also I suggest getting a more proper UVB setup, MVB's are way to narrow for the health of beardies so they mostly work only for portable basking spots or back up lamps.
They are also really dim, while tube lights are more bright and produce a better lighting in the enclosure along with better UVB in a way as its wider and less narrow and you can have high levels, low levels and moderate levels of UVB areas throughout the enclosure instead of just one area with only one single UVB level as if you get it too close to try to provide more levels the beardie can have over exposure when it basks as they do produce a lot of UVB... but only in a narrow beam that doesn't spread out evenly.
Personally i'd go with a Reptisun T5 HO 10.0 for the minimum, i do however like the Arcadia T5 HO 14% lamps and use them for my beardies now in their 75 gallons. With these bulbs generally they need to be replaced every 6-12 months. the 14% Arcadia bulb possibly to 12 months mostly.