I first noticed this egg had zipped around 2:00 am. At 7:00 am, there had not been much progress, but I could see it breathing through its beak. Two hours ago the beak was closer to the surface (that's the white spot in the picture), but not much progress since. I've read its best not to intervene, but I have also read hatching should be fairly quick after zipping. What should I do?