I have a lot to mull over on having multiple litters in a single tractor. Both does chose the same nest box (I provided 2), and the babies all merged. The Lionhead had 5, the NZ 12, and now, 2 weeks later, we're down to 11. The strongest were getting fed twice while the weak were not getting fed at all.
Here are the 8 NZ/Amer. Chinchilla crosses. There's still quite a bit of difference in sizes, but they're all getting full tummies now and look alert and healthy.