Hi all, I have one egg (out of 12!) that has not hatched. It was due four days ago, and all others collected on that day, and for the next four days, have hatched or pipped. This one shows no movement. When I candled it shows a defined air sac and black on one side and clear on another. I don't want it to explode in the incubator, but I'd feel horrible if I gave up too early. Any advice?