I can see veins. I can also see what looks like a really thick vein, like a clot of blood. The chick hasn't moved since Day 21 (no wiggling eggs). So I waited and chipped away the shell today. There's a yolk sac, still. What do you think is the cause of death if they are dead? This is my first time incubating. Any help will be greatly appreciated. I'm sad that they're not hatching.