with my rabbit's babies, I just checked their bottoms every couple of days and just picked off the poop of the ones who needed cleaning. My friend has had a few batches of Kit's born, and he just checks their bottoms every couple of days just to clear away the stuck poop. I think if their poop isn't runny or soft it is fine. We sometimes get a warm damp cloth and give them a wipe to kits that have an extra poopy bottom.
As long as their poop stays firm and their bottoms stay clear, they will be fine