this may be the case, I'm starting to think the golden dorado nipped/bit him in the grow-out tank(the main reason i pulled him to the main tank), caused some wounds which developed into fungus. I'll try if i can scoop him out to put in a hospital tank, otherwise I'll try the UV clarifier method and up the water change schedule.I've had fungus start at site of wound and then pop around the fish at areas with a minor scratch. Would not clear in main tank with mods. When moved to a hospital tank same meds worked. I think the fish couldn't heal with the stress level.
btw my starry night is ok, probably because he's not the tank boss but my 9' oscar is.