Humidity can be a pain when you are running the air conditioner. After a few days you can do a eggtopsy if you really want to know what happened or you can do a simple float test then discard the fails (by day 19 any that didn't hatch should be a fail). Good news is there's always more eggs when...
Sorry if I lead you to believe that 6hrs was the limit. In a idea world food/water with in 6 hrs of them drying off is the best practice but in reality who ever has hatched gets moved to the brooder before work and the rest wait till I get home if yellows not about.
With chickens its best to...