reptisun 5.0 its a bit away from his enclosure as im using it for my veiled as well. roughly 12-15 inches away. his enclosure is leveld so that uvb will penetrate through his enclosure as well as my veileds.
are you keeping him in glass or screen what is the humidity? Also you should provide some kind of air circulation not a breeze if its in glass. I would also suggest a shady end of the enclosure.
I'm new to chams, but is it possible that he's just shedding? Because I think I heard from someone that they sometimes have trouble opening them while shedding. Then again I could be totally off.