Our temps and humidity were rock steady at 99.5 and 40% all through the first 18 days for incubation for this hatch. Last hatch we had tons of trouble with temps and humidity creeping up. Both hatches we've had a handful of chicks that were so big they could zip themselves out of their shells. They pipped and sometimes partially zipped but were so crammed they couldn't finish. These were different breeds form different sources so it's not a genetic thing with one line of birds.