I've never had any issues with hatching my own eggs and all of the chicks end up being happy and healthy in a brooder before sale or moving outdoors, but I keep having this issue where some chicks externally pip away from the air sac. In this week's hatch, 4 of 10 eggs hatched like this (I included the pictures of 2 eggs exhibiting this). In the week prior, 7 of 12 hatched like this. It doesn't seem to matter because they break free and behave/function normally, but am I doing something to cause this? I rotate my eggs 5 times a day until day 18, maintain humidity and temperature, and position the air sac end of the egg slightly upwards. Like I said, it doesn't seem to be an issue but like is this due to external factors or the environment, or is this hereditary, or maybe something else all together?