That is what wiped out my fish in QT. It started with the clown, so I was thinking Brook. I began treating with formalin baths. Few day's later, Blue Regal got it. Guess chasing the clown with the net stressed him out. Treated both with baths. Never saw anything on the Flame angle. Then he stopped eating. So, decided to use it in the tank. Everyone started eating. Then the clown got worse and died. Next afternoon, flame was dead. And today, the Regal is gone.
So I guess tomorrow I'm going to treat the tank with SeaChem's Cupramine and paraguard. Hopefully that kills it so I can start over without a complete recycle of the QT.