Okay update. Today I came home from work and found 6 dead fish. My large beloved rainbows all dead. Further look, all my Cory cats eyes are eaten out.... so I took the tank apart. Did a major water change. Took out every single aggressive fish that I could possibly own. Now I'm left with Pristilla tetras, 2 black ghosts, some corys, 2 clown loaches, 3 smaller rainbows, and a roseline shark... I'm thinking my issues stemmed from some aggressive fish, picking off my fish 1 by 1 .