help to id white spot on purple tang

[boots]

i have just put an purple tang into my system and he has developed a white spot on his side.the spot is about half the size of a dime,slightly raised .my cleaner shrimp cleaned it off yesterday which left a slight discoloration underneath and it seems to be back again today.the tag also suffers from labored breathing and not quite as active.If anyone could shed some light on this it would be great.i hope that i am just paranoid and that it is just some ick.


thanks
boots