My zebra danios have recently become sick. I've lost 1, and I'm sure I'll be losing another shortly... Their mouths are rotting off... They're in a take that has been set up since July 5th, they were the first in the tank... 4 weeks later I add 3 dwarf gouramis from the same fish store, no problems... 2 weeks ago I add some peppered coris from a different store... no problems til last weekend... I notice some of the zebras were hovering in the tank, no swimming like their usual, then all but one stopped a day or 2 later... Then the first zebra I lost seemed to be gasping, so I added airstones, didn't help, he started to shiver at the back of the tank, refuse to eat, & continued what I thought was gasping... Tuesday morning his head was red a bloody looking & his mouth was torn up, I scooped him out & put him in a cup & he rolled around the cup for a while before he could orientate himself, then about 30 min later he was dead... I thought it was isolated just him, but one of my gold zebras is now presenting with the same symptoms, and looking at him, he's missing the top of his mouth & his head his turning red... I think it's an infection, but I'm not sure what it is, I've been looking online all week and the only thing I can find a similar picture of them is for a mouth rot that's supposed to only really infect wild caught fish... I don't presently have a hospital tank or water parameters, I work such hours that the stores are all closed, I'm going tomorrow morning... My gouramis & coris have no symptoms & look great... I don't want to treat the whole tank, but I think I'll need to just to be sure that no one else gets sick...