I hope this doesn't make things worse for them, but I added my four female guppies for the time being. I figured that more fish would be more confusing for them and that they would stop picking at one another.

They haven't established a proper order yet. They go to one another, flare, and one will face the other body-on instead of head-on. It's kind of like them making themselves appear bigger, because they stretch out all of their fins.

The one who has the least amount of damage is Indi, who happens to be the smallest. Zippy, who was once a VERY TINY fish... grew into a monster of a fish, assumedly so on her diet of guppy babies from living with the guppies in the 20 gallon. She looks like a trout.

I'll take some photos as soon as I can :)