Splitting the nest / rotating babies?

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!

Check if they are being fed by checking for a milk band. At that age you can see if the milk in their belly.

She probably does and you just don't see it, usually if a female has too many babies and not enough milk to feed them all she will cull them.

If there's any trace of a milk band on the bellies, she's feeding them.

If one mom has too many babies I'll sometimes take some to put with another mom with less babies. Normally that doesn't cause any issues but some moms will reject babies that aren't their own, so it might be a risk. I normally only remove babies if mom looks thin and giving her Ensure-soaked food hasn't perked her back up.

I agree with the others about checking the Milk Bands.

If the larger group doesn't have any milk, combine the piles or distribute some of them among other nursing mothers if you have any.

I have noticed some females will split their babies into two or multiple nests so its easier for her to feed everyone.

If a female is having a hard time nursing all of them, or generally neglecting them all, I will move them to another bin with similar sized babies.
My moms seen to not care, and will pick the new babies up to move to the nest without me having to scent the babies.

This will all depend on your rats and their natural maternal instincts. It is either genetic or learned, so I will put hold back females in with my good moms so they learn how to take care of babies, build nests, etc.

I've noticed that too with my females. If I put one experienced mom in with some new moms, they all seem to take great care of all the babies. If it's new moms without any experienced moms, sometimes I'll have issues.