NOt for sure if it was the problem but keep in ind what I said happened to mine. Basically eating meaty foods is very unhealthy for tangs. It's like living off fast food alone for humans. They are not built to handle those types of foods in nature. They eat continuously throughout the day nipping at algae. After my losses (I was told they were super easy fish at time of purchase) I began reading about their diet needs and swore off buying them ever again. Of course I also read that a few never had those troubles but the majority said that in the wild they never have a sense of being full from their diet. they must graze all day long. In our tanks when they eat meaty foods they suddenly trigger the "full" feeling and will no longer graze. They eat the foods but actually starve to death as their diet needs are not being satisified.

I do feel your loss as they are beautiful and interesting fish.