I have been trying to hatch call ducks for a few years with minimal luck. I can get the eggs to develop right to hatching time, but then the ducklings don't hatch and die in the shell. I'm convinced this must have something to do with the humidity in my incubators. I usually hold them about 50% for the first 2 weeks and then drastically raise it to about 80% the last 5-7 days. Any suggestions from some call duck pros?