Well something that could stunt his growth is not enough light or not enough food. But you should contact a exotict vet because if you dont get him checked your breadie has a chance of not making it, if he/she has a serious medical problem and he doesn't get checked.

I almost lost my dragon a few weeks ago and the exact thing was happening. In my case it was lack of UVB and he was extremely calcium deficient. You need to act fast. In my case the pet shop sold us a UVA bulb and told us it was all we needed. WRONG. They must have UVB. His symptoms included almost no growth, wobbling, and not a good appetite. I barely saved him, I used rept-aid as an emergency dietary supplement to give him nutrients and immediately put in the right bulb. It doesn't sound like he's getting UVB and/or he deficient because of diet. But there's no way to know unless you can give a breakdown of the entire vivarium. There are many factors when setting up their homes: temperatures (basking and non basking) UV's, substrates etc, diet. If any of these are off it can make for some sick little dragons. My suggestion is to head over to beardeddragon.org and go to the forums. Post in the ER section and you'll get immediate responses from people who really know what they are talking about. They will help you help him. Best of luck to both of you.

i always tell my customer to make sure to have the UVB strip light for them, also if you have one make sure that there is not a clear plastic strip over the bulb, this actually makes the light useless. thats what happened with our male when we got him and he ended up with a calcium deficiency. if you cant get him to a vet then get the supplement already mentioned and another one is the liquid bone aid. you can get this on reptilesupply.com and it works wonders

This is obviously metabolic bone disease. And from what you described is a moderate type of MBD, which is not that great. I hope by now your beardie is in optimum condition. If not, I want to add that it can get worse after what you described, much worse. I completely agree with what was said about not having anything, not even mesh screens, covering your uvb bulbs because they can filter the uvb. Diurnal reptiles, especially desert ones, require uvb and uva. They also require calcium and D3. Bearded dragons are very susceptible to metabolic bone disease, as are leopard geckos. But leos don't need uvb. Their disease is brought on by improper vitamin intake. I hope that helps future reptile owners research their reptiles before they buy one. It would have been great if you gave specifications of your set up. I'm most worried about vitamin intake regiment and type of UVB bulb. If you're a zoo med person, you'd need Reptisun 10.0. You can also use any type of mercury vapor bulbs. Or if you're a Zilla person, you'd need the 50 desert series. I personally prefer the latter, as I find them to work stupendously. Whichever bulbs you get for a bearded dragon, always remember to get long tube lights and avoid compacts or coils at all cost.