Mummy rabbit biting and baby rabbits?

It is not too early at all if they are big, and eating and drinking on their own. My rabbit had a litter a few months ago and the babies were so big, they became like little parasites, eating her food, jumping all over her. I separated them at 4 weeks. They also hump each other all the time, reguardless of if their neutered, male/female, young/old, etc. I love baby bunnies, and just had a litter of 7 Hollands born wednesday. Have fun!!!