Duckling died in shell after pipping had massive hernia. Second duckling with hernia

[Rolling Thunder Clydes]

I have been hatching hens and ducks and have had good success, however a duckling hatched last night and had a large hernia. Another today pipped but then didn't hatch. When I was sure it had died, I opened the shell to find it had a massive hernia and the whole of its intestines etc were inside the egg can anyone tell me why this would happen please?

 

[casportpony]

Welcome to BYC, sorry for your loss. Do you have any pictures? What temp and humidity? What incubator?