I have a powder brown tang that had the same problem. I just fed a little often, and a variety (frozen brine, frosen krill, pellets, and flakes). I also use garlic guard every time I feed. When I make up the frozen food, I usally make a three day supply. I let it thaw with the garlic guard on it and let is sit for about an hour so it soaks into the food. Then I add water with a turkey baster then feed them. It just seems cleaner and simpler. Also, do you have a sump? If so, using calupra will help fight aginst ich. In the past I have tried using reef safe products and fresh water bath, I feel they just strees the fish out more, and your supposed to turn off your uv lights and protien skimmers. If you are planning on adding more fish, like a cleaner wrasse, make sure you add them at night. When you add them during the day, its right in front of the sick fish and it may stress them out even more. So I always wait till everyone has gone to bed and I keep the room and tank dark.
Hope this helps!
but thats only the opinions as a few people, so not a vast majority, il be getting some sunday though 
