Late embryonic death or failure to hatch or high percentage of weak or mutant chicks often results from stress to the preincubated egg or during the first few days of incubation (before the cells have differentiated into tissues and systems, one typo in the genetics of the first few cells can cause significant errors from all the cells that result from it). Shipped eggs, eggs older than 10 days at incubation, heat or cold exposure for several hours, incubator heat spikes, are all possible factors. Sometimes you can figure out what happened and sometimes you can’t, but don’t give up! A bad hatch happens to everyone, I just hatched 3/18 due to a bad turner I didn’t catch until I found 50% day 3-5 dead embryos on day 12 or so and the one before that was 25% on shipped eggs (saddled air cells) half of which were like your poor birds, I even tried helping out 3 and they all died, were weak and underdeveloped. Learn what you can, but focus on the live ones and not the dead ones!
