What did you clean his tank out with? Maybe if there was a cleaning solution used (i used to use 10% bleach)the fumes weren't all gone yet...hmmm was the stuff in his viv also disinfected?
The only reason I am hung up on "smell" is when Digger was 2 we had gotten grapewood (think that's what it was called) from the pet store and I forget what happened but it wasn't disinfected and after about 2-3 days Digger looked horrible, shrunked, stress marks,
black beard and we had everything right temp wise, so by process of elimination (I only had 2 things in his tank a log and that wood)I got it down to that grapewood...threw that sucker out and I think it took a week before Digger got back to himself. I made sure his towel substrate was clean too.
I hope he gets better soon!