Orange Shoulder - Picky Eater

[Parker]

My Orange Shoulder Tang is becoming a very picky eater. He used to eat everything from Mysis, Flake, Pellets, Nori but as of the last month or two he stopped eating anything but a particular brand of Flake, which he goes crazy for. He's starting to get pretty darn thin. I thought maybe I would stop feeding flake for a while and just feed the things he doesn’t like in an effort get him hungry enough to eat other food again, but I worry about how thin he is and then might not make it.

Any suggestions?