A couple months ago, I found a dead chick next to the mom, but I was fairly certain she hadn't killed it. It could be something was wrong and it died under her and she pushed it out. She went on to hatch out the other eggs under her and was a terrific mom. Once my eggs pip, they can take a while (several hours) or just a few hours. I don't believe the eggs can hatch without a source to keep them warm. If you choose to remove the chicks to a brooder, you may have to do it as soon as they hatch. Hope the rest of your chicks make it okay.