I cracked open a rather long egg tonight, expecting a double yolk, but instead a clump of blood came out- no yolk. Upon further investication I found an air sac and a wrinkly bit of shell at the top exterior. What could this be? I know the egg was laid today because I collected last night. It did snow and rain today, could that be a contributer? Also, my flock is sick (we haven't been eating the eggs) and are undergoing treatment (they are getting better and better each day). Again, what is it, and do I need to worry? Please tell me what I need to do to prevent this in the future. 
