It looks like it might be a duck egg to me..... is there any possibility it could be? Do you have any ducks or were these bought hatching eggs.
If it was a chicken egg I would have expected the blood supply to have shrunk back by now, but I am no expert on incubator hatching.
X2 I instantly thought that after seeing the day it was on and what the shell looked like. Have you seen if there is still the yolk sac attached to the little one? Unfortunately all I can suggest is keep a close eye on it, and if breathing gets weaker, then open it. It could be the babies only chance. And remember! It is not your fault if the little one doesn't make it. You didn't know it was a duck egg, and it is not your fault. Wishing you luck, and keep us posted.