Hi, I just went through my first set of eggs on day 10 and removed the bad ones. Most had not even started to grow, but I didn't see a bulls eye. Does it deteriorate as the egg ages if the chicks do not develop? These were shipped eggs. Or could they have been fertile, but the Mail shook them to a point of it being no longer visible. ? Or, were never fertile to begin with.? I'm new to all this and have so much to learn!