Chicks don't read the manuals. Your incubator is probably running just a bit low. Or are you a serial candler? Was the first day you put them in day one or day zero. It should be zero. If you open the bator a LOT you can affect temps to the point you slow a hatch. If your temps run a half a...
I've had awesome hatches of shipped eggs and zero hatches from shipped eggs, I rarely incubate that I don't have at least 40 eggs from 2-6 sources. Shipping will always decrease your odds somewhat, depending on temps, postal gorillas and luck. It always is a gamble.
Since I have eggs from...