And Katy, you are correct....I have the eggs in the turner small tip down, so the air sack actually is at the top...Again, I'm not a very good artist and I created that visual out of the other picture on this post in less than one minute, so it's no where near anatomically correct!!!. I just wanted to illustrate what the weird dark spot looked like so that you'd have some type of reference. Hope I'm not confusing things more by drawing bad pictures!!!
Here's a (real) picture of one of the eggs that I just candled...This is the best shot I could get. Do you think it's just the embryo, or does it look abnormal?