That's good to know. Now, how to get them a bit more oxygen...Don't be in too big of a hurry to buy into the higher humidity at higher elevation proponents.
4200' isn't that big of a deal. It's the ones that are over 5000' that have more of an issue. The issue isn't the humidity but rather the lower concentration of oxygen. Especially the build up of CO2 when a lot of chicks are hatching at once.
I'm at 5200"+. I incubate at 30% to 35% humidity if I can. I lock down at 65% to 70% humidity.
I just watched my mail carrier throw the box of Myshire eggs towards my door.