German Blue Ram Behavior/Territory issue

[Noveria]

I have 4 german blue ram cichlids in a 37 gallon tank. Originally I had 2 females, but a couple of weeks ago I decided to put a couple of males in as well. They were getting along great for a while. The more similarly sized ones paired off in M/F pairs (larger with larger, and smaller with smaller), with one pair taking one side of the tank and the other taking the opposite side. However, a few days ago, the larger male suddenly appeared to have decided that he didn't like his mate any more (larger female). So he has driven her out of his territory, but she doesn't have anywhere to go because the other pair still has the other side of the tank, and they won't accept her either. Any idea why this might be? The only thing I can possibly think of is I had 3 guppies, and they had 7-8 fry not too long ago, all of which have been growing steadily larger. Could it be that he feels more crowded now that the fry are larger (though they're still only a few weeks old and far from adult-sized), and thinks that his territory is now insufficient for two? He has also begun showing aggression toward the other fish I have, both the guppies and the neon tetras, where he hadn't previously. Or is it simply that he doesn't like her any more and I need to switch her out for a different one? Any advice/suggestion is appreciated. Thanks!