I ususally hatch Khakis and regular Pekings, and they aren't like quail, they come all at different times, except in very large hatches (of say 50) where many come in 24 hours. There is always a first, and a last (if your lucky) and one might have been closer to heat source, and is ready now. The ones toward the dead center can be slower. It just works that way for me. Perhaps this is the explanation.
I have some special Jumbo Pekings baking, and I'm worrying over them constantly. I really want them, and I've only 7 of 13 original eggs. Seems like every 3 or 4 days, one goes south. I don't lockdown until the 21st. My last hatch (turkeys and quail) went south after an egg blew up. As a result, I've started candling more. I've bleached, I used a new bator, I'm monitoring like every other die hard hatch addict. I think I'm gonna go have some leftover green beer.