what to do

Not quite sure what's going on with my oto. He is one of three, the only one of three, to show these "fuzzballs" on his back. I'm not sure if its columnaris, or something else? It doesnt seem to match what I can find of columnaris either. I noticed one spot, a few days ago and thought maybe an...

As title states, guppy developed strange lump on chest/stomach area, ONLY on the right side, the left side looks perfectly fine. The only thing they have had to eat today, is finely powdered flake food, or whatever they scavenged off substrate. Only one to exhibit symptom. Have secluded her, as...