What the hell is this

[boltenhanics]

Water is cloudy from a fungus medicine my dad tried to treat the tank with, he just hasn't been able to completely get it clean. Parameters are totally fine and it only seems to be affecting these fish. We don't know what they are, they came with the tank when we got it ~4 months ago. These have started popping up slowly over the last month

 

[fluttermoth]

It can be very hard to diagnose fish diseases, but I would put my money on that being a bacterial infection.

Can you post the actual numbers from your tests, please? Nearly all diseases in fish are ultimately caused by poor or 'wrong' (for that kind of fish) water.

That is a rainbowfish, although I can't place the exact species, and they usually need hard water to do well.