My friends Chevron Tang is doing the same thing. If your fish is still eating and no one can give you any clues then I wouldn't try anything drastic. A fresh water dip may be in order if it is a parasite. If it's not ich or marine velvet then I don't know that there is any way that you can treat the fish medically. I hope you get an idea, I will keep watch for my friend also. i hope your fish makes it and that it's just one of those things that pops up and then disappears just as quickly. Keep us posted.

Angie