You are running the humidity too high during the incubating period. The correct humidity can vary by location, generally, 55% to 60% is high enough although one year I had to run at 45%. Start weighing your eggs and aim to lose 10% to 15% of the total egg weight by hatch time. 75% is a good humidity for hatching although if you have a lot of eggs hatching at the same time the eggs themselves will spike the humidity until you open the door.