My four gliders were coexisting together just fine for about a week, but then quite suddenly my two females started fighting, and I mean balling up and biting. Thankfully neither one was hurt, but I've since separated them.

I've been swapping pouches once or twice since, but have not tried them together again as of yet.

Is it possible one of the females is in heat and that could explain her sudden behavior change and intolerance towards another female? The two males in my colony are neutered, for reference.

It is likely being in heat. It could also be hierarchy is being challenged. The pecking order in a colony goes through this periodically.

Are one of the females the Alpha?

When you say separate the females, are they each in their own cage alone?

I'm not sure which is the alpha. I currently have one female in a cage by herself and the other with the two boys. Should I separate them differently?

I stuck one of the boys in with her, so now she's not alone. I believe she is now in heat, too, though. Any suggestions on what to do next?

Ideally, I'd like them all back together but I realize that may just not be possible.

That sounds like a good idea, now at least no one's alone. I don't know, maybe giving a cool off period, then begin the pre-introduction procedures.