I finally been able to tell which is prego so I put them in a new tub. I put 4 in one 15" x 22" tub and now at least 3 has given birth and they seem to be doing fine.

However, there is another tub where I moved in the mom and her pups after ther were born. At the same time, moved in a prego from the same group. Then few days later moved in another prego from another group. I heard they had some minor fighting for a little while, then quite down. I thought only one was showing authority.

A couple days later another mom gave birth, I don't know which one. Then I found that all the babies were moved together (by the first mom I think). The next day, all but one of the new borns were dead.

Did the first mom do this on purpose?

Am I not supposed to put mom from different groups into the same nursing tub? (but the tub with 4 are all from different groups)

Or is it because of the timing of giving birth?