Rescued a mature Chevron Tang, Need advice

[super7]

The Chevron died, got back from work and it was dead. The other tang I rescued is weird looking, I think it is a atlantic blue tang turning blue, I am not sure and will post a picture of it. I had them in seperate tanks because I was pretty sure that the other mystery tang beat up on the chevron pretty bad. I am (was) feeding both tangs nori and formula one herbivorous pellets.
I will try taking a pic tonight and post it.
Thanks for all the help, really apreciate it, sucks that he died.
Super7