Keep in mind that I am not an expert, not even close, lol. It's head and neck look very swollen, and I think that might mean that it didn't lose enough moisture. I have seen this a lot in artificially incubated chicks, never in broody incubated ones.Like this?
Based on this it has to be nutritional deficiencies.
Keep searching. See if you can find causes for that swelling.
Hmm
When I say heat stress is not an option..I am dead serious that it is not an option.
Extremely high.
Maybe? If you decide to do this again weigh the eggs and shoot for whatever the industry standard loss is. Let me use my pea eggs as an example. If my pea eggs lose any less than 14% they will have some swelling on their heads and necks and they will have huge yolk bellies. Those that lose 15% or more look much better at hatch.
