Hi, my Dominique in my breeding pen and my barnevelder and my olive egger... The shells on their eggs are so dark. I want to know if they're fertile and the Dom eggs are in the bator. I know eggs are fertile from my other rooster but I'm selling him and hoping that the other guys are doing their job. But I cannot see into the eggs to see veining and I don't have any other monitor. I can see the shape of the air sack and sure I could wait it out but what exactly am I looking for when I look at the eggs for any other signs? I have 5? on day 8? Thanks for any thoughts