Hatching questions!

If you're seeing day 15 hatches your temps are probably too high. Double check your thermometer with a different one. You could of left the racks in they don't hurt anything most times.

You should never open the incubator when you have pipped eggs. Any eggs that holes in them when you opened the door are most likely not going to hatch at this point. The spastic influx of cold air into the incubator causes the inner membrane to harden and the chicks most often can't escape their shell after that.

After lockdown you shouldn't open the door again until you are removing chicks that have been fully hatched for 12-24 hours (they should be dry when you pull them out). Chicks can easily survive 24 hours in the bator, they absorb their yolk more slowly than many other species and often wont eat for part of that first 24 hours even if you put them in the brooder.

I leave my chicks in for closer to 24 hours before I remove so that I don't open the door when any eggs are pipped. If one hatches early, too bad, it's got to try to survive until the main hatch happens. It sucks but it's the greater good versus the good of the individual chick. The chicks communicate in the shell to organize the hatch so the most of what will hatch is going to come all at one time. Until that large wave hatches and dries completely out, my incubator stays closed. I've not had a chick die from being left in the bator that I can recall, and I've had to leave early ones in for 30-40 hours with no ill effects.

Don't try to help any that are having a hard time hatching because most often you'll mess something up. It's easier to kill them than save them that way and most often when you help a chick out of the shell you'll just have to euthanize it later for development or health issues. From the time they pip or break through the shell, it can take up to 30 hours for them to get out of the shell completely so be patient.

Good Luck!