Female fancy mice are fighting when socializing, what should I do?

My 6-colored female mice that I'm currently socializing are fighting. They don't bite each other, but I'm worried that will happen soon. It always happens when they sniff or feel each other around, which the others don't seem to like. They start to squeal. I don't know. Should I separate them or make the enclosure smaller? Why are they fighting? Do you have enough space? It seems like they just want to sniff each other, but then they start pushing each other. I'll do it again and they'll fidget a bit. This usually happens in their sleeping quarters.