He seems to be feeling better. He is active again and even made a bubble nest, his first one since he's been here. What a weirdo. Anyway, I'm not feeling too confident that this is Velvet after seeing one with a really bad case at Petco. Right now he is in a hospital tank, in a dark bathroom, 82 F water and no salt. Still using coppersafe.
Something I noticed (which may be the real problem or related to the coppersafe?) is his gills are very red and seem to be sticking out more than normal? When he takes air at the surface of the water his gills actually make a noise, which is odd.
This picture shows the stuff on his face, which I'm unsure if it's related to the illness or just him developing more color. He is a Marble, after all.