Someone I know has chicks hatching under a broody that are dying halfway out of the egg or immediately after they hatch, even up to the point they get to the brooder, then gasp and die. I may not have all the information you need to help here, but I told her I'd ask and see if anyone had any thoughts on the possible cause. The only things I can think of are some ecoli contamination in the nest and/or on the eggs that has spread to all the chicks. She has a previous hatch where there was sticky goo and a "cheesecloth-like" substance on the chicks. The only possible causes I can find are nutritional deficiencies in the chicks/breeders OR just bacterial contamination of the eggs/nests. Anything else?