When I incubate eggs almost all of my eggs are fertile and grow correctly for the first 18 days. But when it is time for them to hatch I have maybe (if I'm lucky) 50% of the eggs hatch . When they do start to hatch it takes them at least three days for them all to hatch out. Why do I have so many deaths the last 3 days and why do they hatch so far apart from one another? Any help or advice is greatly appreciated and thanks in advance.