I wouldn't divide gals and males because they both release smells, which the male can get stressed, and/or the female can get stressed. You may need to rearrange your tank completely, do a water change with gravel siphoning, add conditioned water, and float them in cups. You can tape the cups to the side of the tank, beside each other. Let them see, but not touch, if that makes sense. Acclimatize them, then add them to the tank. Lost fins are very common when they begin to choose a new alpha. Because you removed the imposter (
that lil'male!) you've set it so everyone had to remake a group. So it would've been normal to see that aggression! If no one is infected with rot, fungus, and their bodies themselves are okay (no wounds) you can re-add them all.
I found when the large gal I got attacked Marge (Marge is no longer alpha....) I fed them all. They stopped to eat, and with the food spread out they didn't fight for food. After, they've gotten along.