I disagree with
@Sundragons. I have been raising rabbits for a while and I find that the doe(s) should not be bred monthly, monthly mating will shorten her lifetime by a couple years if you continue to do it this way. Also 30 days is far too young in normal circumstances (I repeat NORMAL circumstances) in a case like this where the doe is delivering another litter, yes, remove them and put into a transition cage,
not with the buck. I would not suggest monthly matings, the previous litter will always have to be removed at 4 weeks old, which, as I said before, is far too young. I have been raising meat and pet rabbits for many, many years and always wait to wean until at least 6 weeks old, if not 8 weeks, depending on the doe and size of the litter.
If you are interested, I can share my breeding schedule with you. It is very exact and leaves just the right amount of time for the does to rest between litters, while still getting a decent amount of meat growouts and/or kits to sell.