Day 15 are they okay?

[lilgreencoop]

I am on day 15 with ten eggs in the incubator. Candling the eggs was perfect up until day 10. Development was great...we could see movement. Come day 15 the eggs are so dark inside you can hardly see a thing...including the air bubble. Any ideas as to what happened? Imagining for the best. This is my first hatch.

 

[ChickenRaiser95]

dont worry that happens, its just the embryo is getting bigger and thus harder to see. here is a link about chick development:
http://msucares.com/poultry/reproductions/poultry_chicks_embryo.html