I have been filling my incubator with eggs from young pullets who just started laying. All these pullets were in breeding pens with a rooster. None of their eggs have development after 7 days. I always check the eggs at three days and even though I didn't see any veins I left them in. I just cracked them open to check for fertilization and all of them were definitely fertile. Why would they not be developing? Because they are the pullets first eggs??