While that's entirely possible, even probable in most cases... i know this tang has been at his store for a couple weeks and was healthy last Friday when i was there. My friend is not the only one in the store and he has a hard time keeping up with everything that pops up, especially when the others that take care of the fish when he's off don't always do the things they should. After i posted the thread i kept looking and that entire system is sick with something. Some fish look like they have brook or ick or any number of things. SOMETHING must of happened to cause this. The tanks should be running with copper and hypo salinity to keep some diseases at bay.
I don't have a clue what this white bump on these tangs is and I'm really curious as to possibilities. It was just the kole tangs (3 total) that have it, all in separate tanks yet on the same system. When he orders my fish I'll be picking them up before they come out of the bags for sure.