lost yellow tang to a green bubble anenome

[geweagle]

There was a red region on one side up near the dorsal fin. Not a scrap or line but a region, sort of like a red bruise. Never saw it before. It was very strange because it was so sudden. If it was a chemistry issue I would expect to see the fish in stress before and adnormal behavoir. He was fine. Also all the other fish in the tank are all fine and no sign of stress.

I agree it is strange. Even today all the fish seem normal and were active when I feed them.

No sure and likely will never know for sure.