That is definitely an interesting looking skin issue there.
It really could be a burn, or that is what it appears to be. His back area may have been getting too hot somehow.
The UVB looks good, is that where it has been for the last several years?
How is he doing today?
I hope the silver cream works well for him.
Yes, all the lighting, etc. is the same since I built the habitat. The only difference is the log I put in about 2 years ago has been removed. He does seem to be doing better and has been a little more active. I think he's missing his log that he'd become attached to, but, that's the way it goes. I'll have to try to find something a little lower. Today I get to give him another injection of antibiotics. Also another soak and more cream.
I am glad to hear he is doing better! Poor guy, he loved his branch. Maybe you could hold onto it & use it at another time, perhaps.
I hope you find another log for him! How did the shot go at the vets?
Let us know how he is doing!