Help two fish just died, what is wrong?

[cambeck510@gmai]

2-3 days ago my heniochus butterfly started to develop charcoal colored spots around its head. a day later its dorsal fin started disappearing (almost like being eaten away) and I placed it in a quaranteen tank. today it was dead and one of its other fins had started to disappear. I seemed to have dark spots on the white areas and light spots on the black. A blue hippo tang also died. It looked like the color had faded out of it, but nothing else obvious. Other 6 fish in tank are okay, water check is okay, and I do run a UV light filter.

Any Ideas? I've searched all over to try and figure it out.

Thanks for any help

 

[snorvich]

History of fish? Quarantined?

 

[mattcoug]

Is this a new tank? What does "water check" mean?