Well, that's a tough one. Didn't you say they fight over treats? Do they get that in the a.m. or p.m. I'd say bribery might work....a little parsley perhaps every afternoon when you first get home.....it almost sounds like a game they are playing.
Too, make sure you are sitting on the floor, they might not like you leaning over them (you're big and scary even if you are the mom).

I continue to have some good luck with holding Chocolate's head down so she knows I'm the dominate bunny....it's not been a cure all as shje will occasionally go after Miss Emma, but she's not as bad as she was.