Kole tang question

[The Guy]

My kole tang usually grazes the tank and eats nori, pellets and frozen mysis like a little piggy, but for the last 4-5 days he hides out in the rock work and does not seem to be eating anything.
When I managed to get a look at him from the end of the tank his mouth seems to be open and quite white looking, I read that because of their mouth structure being full of bristles Koles can get growths on the inside of their jaws that can cause them problems, he seems to be able to open and close it somewhat but won't eat which concerns me. He's been in my new RSM 250 for about a month now and did notice his color looked faded a bit and thought maybe it was because of the new LED's on this tank, but the rest of the fish look fine.
Any suggestions or thoughts anyone.