Perhaps the parent flock has some inbreeding going on.
I did eggtopsy and unless underbites are what happens when a chick drowns... Looks like that would've been a deformity for four of them had they hatched (or perhaps the underbite prevented them from pipping!)
I did also notice that every chick who died in shell was positioned strangely so had they been able to pip it would've been in the middle of the egg, not in the air cell.
I've not eggtopsied such fully developed chicks before. Is it normal for them to have one foot curled up and the other outstretched completely? This was a common theme in all eggtopsied today.
Both legs should be tucked up by the head, like behind the "ears". I wonder if it is part x-rays and inbreeding that cause the deformities. I don't inbreed, even a single generation, so I don't know...