I know you already know to keep the water clean and I'm sure you are.
At this point, the tank should either be completely bare of items they can claim as territory or there needs to be enough places to stake claims for everyone.
When I had a BUNCH of babies in a 10 gallon, I just put in a few pieces of PVC pipes both elbow and straight shape. It gave the ones being picked on a place to hide anyway. It was also a great way to catch them when I needed to because all you have to do is cover up both ends with your hands and you've got them.
Good Luck with the rest. You've achieved a lot to make it this far.