Sorry for the lack of responses folks, I've been a little busy and pretty sick this weekend.
So it is day 4 for the O Shamo, and day 6 for the others.
I've done some candling, but I don't really see much activity to be honest. Some of the shells are a bit difficult to see through. The O Shamo though are pretty easy to see.
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This is one of the Black Australorp eggs. The pictures not so great, but there are small veins forming.
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So what does it mean when an egg is dark? I don't mean to shell. I have at least three eggs that I can see light coming up through the air sac, but everything between the sack and the light is just a shadow.