Mine had a 100% hatch, too!
You will see mama broody keeping her babies under her when it gets really cold...mine would migrate the whole flock to the feed dish and hover over the top of it so the babies could eat and not get out from under her wings. She hatched them during the single-digit negative-digit days![]()

Now I think I am almost ready to try to hatch some with a broody, if they can survive these temps with mom, they'll be fine.