Rescued a mature Chevron Tang, Need advice

[super7]

I picked up a chevron tang in really rough shape. It was in a dirty tank and has a lot of color loss. I am Quarantining it at this moment but was wondering on what I should feed it to get it back to black instead of white between the caudal fin (tail) and body. I am feeding it Nori and the Q tank has live rock, for now, for algae. Is there anything else. I will probably put a UV filter on there too.

Sorry for the rant but, any suggestions?
Thanks Super7