I've noticed that a couple of my fish seem to be turning black. It's not like they're being covered with something, more like the scales themselves are darkening. The darkening seems to happen around the face, while a few of my Columbian tetras have black blotches. I've treated everyone for parasites/intestinal pests of every variety and have started them on kanamycin antibiotic food. Everyone is eating and behaving normally.
This could have something to do with Bub, my blue gourami who had a bacterial infection a while back. He was removed to a hospital tank and treated until all his booboos healed, although he continues to have swim bladder disorder. While this makes him rather buoyant and he spends all his time at the surface, he still gets around well and eats heartily and I don't have the heart to put him down.
Columbian spots
Flag fish with darkened face
Can anyone name these spots/blotches? Any and all input is appreciated!