My yellow tang is being weird. He's stopped eating much and has what looks like a pinkish rash on his flanks. I've had him about a year. Nothing new has been added in months and everything is quarantined 6 weeks before it hits the display so I'm doubtful that it's parasites. Other inhabitants are fine and so are water parameters. He does seem to be attacking and then hiding from his reflection more lately. It's hard to get a photo. He used to pig out on Nori and barely touches it now. Any advice?