Not ICH or Velvet

Okay, here's the deal. Cold Has a Blue Damsel he hates but doesnt like to see them in anything except perfect condition. This Damsel is turning white from a little in front of the anal fin all the way to the tip of it's tail. It is snow white and spreading to the front part of the fish. I noticed it starting to change it's color a couple week's ago. It is a slow gradual change but look's like ICH or Velvet. The fish swim's fine and eat's like a wild boar hog. The fish show's no sign's of any kind of illness and is not rubbing up against rock's like fish with ICH do. The other fish in his tank are a Yellow Tang (small) and a Pigmy Angel a Pajama Cardinal and two bluegreen Chromis. None of the other fish are affected at all. I know the Tang and Angel are very ICH prone fish but have no sign's of any problem's at all. I can not get pictures sorry. Just a description. What else would make a fish turn color's like this? It is half pure white. Whatever it is is very thck on it's scales but show's no ICH sign's.
Thank you all very much for your time. And Coldshot is back in the hospital. He say's his heart is toast so pray if prayer is in your list of thing's of thing's to do. (some dont believe) He is a real good guy. He told me to sell his tank and rock's and fish but I have no idea how to do that so it stay's. Okay I got a picture of the fish. The white stripes and spots are stronger in life than the picture. Cheap Camera. I blurred everything out so the fish would stand out more.
GreyGhost

 

Looks like fin and tail rot to me. Not sure what it is really, but I had one like it and marycin cleared it up. I dont like to use atb's, but I tried everything else first. I hope I'm not to late. My prays are with coldshot: I will keep him in my prayers.

 

Whatever it is seem's to be clearing up on it's own.