FYI I had tried balas as dithers in the past and they did not work. The ATFs would just ignore them and kept fighting among themselves, as if they can tell balas are not their own kind. I think it's the balas eye shape or head structure that gave it away.
Anyways, three will surely not work in the long run. The weaker ones might have lacerations by now, and the cut will only get deeper and longer as the bigger/attacking ATF grows. If you add more it will make the situation worse, unless they are in a +300g tank. Even then, it only will last them for a few years and some will still get killed along with way.
My only advice is to separate them and grow them out individually until they hit over 18" and combine them again to see if their aggression will subside in their adulthood.