Splitting the nest / rotating babies?

[MrLang]

So the momma that had 17 babies has done something a little strange. She's a first time mom. She seems to have separated 6 babies from the 17 and is nursing them in a separate pile. I read they can do this since they only have 12 nipples. What's strange to me is that every time I've gone in there she is only nursing the pile of 6. I haven't seen her on the pile of 11 for over 12 hours. She could be doing it and I'm missing it, but every time I go in shes hovering over the pile of 6. The pile of 11 survived the night. They're 36-48 hours old. Does this mean she must be feeding them and I'm missing it? I know they eat every 2-3 hours, but how long can they go without milk before they die?

Should I leave them alone? Rotate the 6 back into the mound and let her pull another batch? Pull another 6 that have less visible milk bands for her?

Thanks!