red eye tetra

70 gallon community tank, same issues as last time, out of all of my fish (about 70 small tetras and barbs) only about 5 of my red eyes looks like this. they have big white patches on the top (and sometimes side) of their noses, one of which has lost the white patches but the skin turned black...

I am selling/giving away all of my fish as I do not have the room for the tank in my new place.   The fish for sale are: 1 x Silver Dollar (Quite large, couple of years old, nearly 5 inches in length.) 1 x Bristlenose Catfish (Mouth is a little weird on it, but had it for 2 years now and it's...