So day 5, I decided to candle an egg that was questionable to set in the first place. When marking air cells prior to set, this ones air cell was just a bunch of little air bubbles that moved along the shell as I moved it. I decided to set it, figuring I would end up chucking it. Today I checked it. The air cell still is a bunch of little bubbles, but it is developing. It'll probably never make lock down, but it's cool that it has developed.
These eggs are a backyard mix out of my own chickens. The chickens are older (2 1/2) won't be with us much longer. Any ideas what would cause that?