I have had the worst hatch ever, Out of 12 eggs I have had 1 splash Ameraucana hatch. It was my fault, not the eggs. I have had major humidity issues, and tried to help when I shouldn't have. I just candled the remaining eggs and I am pretty sure they are all dead with the exception of 1, I can't tell for sure if I saw movement or not, but I can see lots of veins on the eggs still, does that mean it is alive still? The others I see nothing but dark blobs. I sure hope that I can get at least one more, so my poor little splash isn't alone.
I would leave them alone through day 25. With incubating problems you could have a delayed hatch. Black blobs mean the eggs are filled with the later stage developed chick embryos.