So it was 21 days yesterday and my one egg piped at around 10:00pm last night. It's now 7:35am and it hasn't zipped yet. Is that normal? I did take the lid off the incubator for a little bit to turn my newer eggs and the temperature was a little low when I woke up. I know it can take up to 48 hrs to hatch but I'm still worried. How long after the pip should they zip?