Looks like black ich.
I found a brief article on it, but I would research and decide how you want to treat.
http://www.wonbrothers.com/product/D...c_diseases.htm
I have ich in my tank and have left the fish alone, feed good food soaked in Selcon and garlic. I did not have a good experience with a QT tank and have not reattempted one. The fish fight it off on their own and I've had no losses.