Kits can start eating solids as early as 2 weeks old. Mind they will not sustain themselves on a solid diet at that age. At about 1 month old they are old enough to eat or forage for solid foods like pellets. Rabbits breed like, well rabbits. Rabbits are - well you are seeing the multiplication problem unfold. Not only should you put mom in her own cage, but you should get rid of the buck or the doe (pick one) and not try to raise rabbits. Rabbit breeding is a fun and profitable business only if you are raising rabbits for Food. Every single responsible website and book on the subject will tell you NOT to raise rabbits as pets. Rabbits are not popular pets - except during easter time when folks think its cute to have a baby rabbit in the easter basket - a month later they think the rabbit is just a large rat (rodent) and they set it free in the wild - which is my front yard - or the front yard of anybody who lives on farmland. Then we get the not so nice job of shooting the rabbits before they multiply out of control and bring pure detestation to our crops, our gardens, our lawns. Rabbits are good eatings, and we have raised rabbits AS FOOD because they breed so fast and are easier than chickens to raise and they provide more meat with the added pelt which can be tanned and used around the house for various things or sold for profit. You only keep a doe and a buck (female and a male) together when you want more rabbits. all other times you keep the separate - preferably in separate counties since they can almost breed with casual contact.

If they have had access to good quality hay and some pellets, they might be okay. It is very early to wean them without special preparations but there is nothing else you can do since you allowed the doe to get rebred so soon. She should have had a rest between nursings but now she will be nursing solidly for many weeks. Be sure to feed her very well. I'd give her some Calf Manna pellets, about 1 tablespoon a day so she will get adequate nutrition. But it will be very hard on all of your rabbits, the doe, the first litter and the second. Please consider spaying her and not breeding her anymore. This is just too much stress on her body and of the young kits.