Skinny Blue Throat Trigger

[Coralgurl]

My male blue throat trigger has gotten quite skinny in the past while. He's eating frozen foods and right now I've been feeding 2-3 times a day. All my other fish are fat and healthy. They did have worms a few months ago, I treated and they cleared up, but he didn't appear to have them.

How do I get him to fatten up? There's been a few times he's gotten stuck to a power head when feeding, but he's either pulled himself off, or I've helped. He's normally an active swimmer, but he's now mostly hanging out in the rocks, except when feeding. Help!!