I have a 10 us gallon tank with 4 neon tetras 2 platys 2 otticinclus and one African dwarf frog. Ive has my tank since the beginning of the year and the last couple months have been rough. One of my tetras got a discolored spot on the red part of his body so we quarantined him but he died from the shock. My fish we’re fine for a couple weeks and one morning the all had fin rot one of the platys died but all the other fish we’re fine. I got another platy and they were fine for a month. One of my fish got the same discolored spot as the other one but he was starting to get better but now all of my fish are sick but the platys are my main concern. Their whole face was covered in what looks like fungus and then I did a water change and they were swimming happily but then 30 seconds later it was back. I’ve been treating the tank with Melafix and Pimafix. Please if anyone could help