Royal Gramma has some sort of skin problem? Or something else entirely?

[jostafew]

Hello everyone, I've got a Royal Gramma that I've had for about 4 months and in the last week has developed a couple patches of what look like missing scales on the top of its body between the head and the dorsal fin. I've tried my best to take a decent photo, but it gets skiddish whenever the camera's around. In addition its appetite has gone from garbage disposal machine to barely eating anything at all. I initially thought it was a result of rough-housing with the Azure Damsel, but after careful observation over the last week I've seen no evidence of the damsel picking on it... in fact it's quite the opposite (as has been normal for the past couple months that I've had the damsel). They're odd shaped patches, one approx. 1/8" across, and another approx. 1/16" across. It looks like bare skin under neath, grey smooth and shiny... No signs of mucus or or cottony substance. Nor does it look raw like it's been rubbing up against something. I don't currently have a quarantine/hospital tank set up, though if required it will get done. (the tank is relatively new and has few inhabitants so I've haven't bothered yet) Anyway, I'm hoping someone has come across this before and can help me figure out what I'm dealing with.

Thanks in advance
- Justin

In the first pic it looks like there's something white on there, but it's just the flash (not there in the 2nd pic)