I've been incubating my duucle eggs from my hen and so far every one has been fertile since she started laying. I've hatched 3 chicks out of 6 eggs so far, a couple I've had to help out, the others died before hatch or during hatch. My question is, the last couple eggs have pipped and zipped and when I check on them again, the chicks are dead hanging out of the shell. The one today had peeped all day but never cracked the shell, so I made a small hole in the shell where his beak was and put him back and when I checked again he was dead too. They seem to get half hatched and start acting like they're choking on air and just die. Any idea What could be going on?