spot on green chromis

[bentrue]

the smallest of my three green chromis has what looks like a patch where the scales are gone. it is a small patch that is pink looking. this one is chased constantly by the two larger chromis, especially the largest one.
is this some kind of disease, or is it the result of constant aggression? it really looks like a spot where the fish has been bitten over and over.
please help

 

[tacks]

Wish I could help. I've had the same thing happen to several Green Chromis. Had been told it was some sort of bacterial infection but I'm beginning to think its specific to the Green Chromis. None of the Chromis that had it made it. Sorry I couldn't be more helpful.