Two Nest???

So my mouse gave birth to 8 babies earlier this week,and tonight I come home to find them separated into two nest.

Is this something to worry about? I didnt look and see it the other mouse with the second nest was a male or female.... The last few days I have been able to see nipples on the second female that I normally dont see.

If they arent back together tomorrow what should I do if anything?

They do it for control. It's easier for them to nurse and clean 4 and 4 instead of 8 little suckers at once. She will most likely put them into one big nest, then back into 2 many times. Nothing to worry about. Mice like to be left alone mostly.