This is the first time I have incubated duck eggs. Yesterday was day 28 and they all started pipping. However it has been 24 hours and they have not started to “zip”, so I am starting to get nervous. When I put my ear up to the incubator I can hear little peeps and I can see and hear the duckies attempting to chip away at the shell, but don’t seem to be making much progress. The temperature has been pretty constant (98-99). I don’t have a wet bulb thermometer which I realize is rookie move, however I have kept the water reserve in the bottom of the incubator full and the the little windows have fogged up. Is this kind of slow hatching process normal or should I be worried???