A hen has to make a choice between babies she knows are alive & ones that may not make it when she gets a staggered hatch. It sounds like some extra eggs got added to her nest after she began sitting. She can't take care of the already hatched babies & continue to sit. You have 2 choices if you want to save the remaining babies. You can plop them in a bator & finish them out or you can take the chicks she has & hope she returns to the nest to finish them herself. I would go with putting the eggs in the bator if she has already left the nest with the other babies. She may or may not return to sit if her chicks are taken. You also run the risk of her refusing the babies if you take them & then try to return them after the others hatch. It's a hard choice, but sometimes you can't save them, especially if you don't have a bator & aren't prepared to brood chicks yourself.