I’m sorry don’t know much about mums and kits, but the new kits are probably the litter of the other doe. You’ll have to check so all kits get fed. You do that by looking at their bellies, they should have nicely rounded bellies after feeding-time. A doe only feeds her kits once or twice per day, and the milk is very high in calories because it’s so very fat. So if you don’t see the does go to feed the babies, they could still be doing it when you’re away from them. Buns don’t lie with their kits like cats and dogs do. In nature, the baby buns are kept in a separate burrow, wrapped in mama-bun’s fur to stay warm.
There is another forum that might be better for your needs, RabbitsOnline. They have a section called the Rabbitry and Showroom, where you can find breeders and others that have experience with baby buns and their mums. http://www.rabbitsonline.net/forumdisplay.php?f=20
I found this web-page about one doe having 2 litters. In your case it seems more likely tat the 2 litters have 2 mothers though: https://www.raising-rabbits.com/rabbit-pregnant-with-two-litters.html