For years, I have tried and failed to hatch out my own chicks. I have changed out the rooster and the hens. All of them are the same sized birds, with only 10 hens to a rooster. I can't figure it out! I have put them under several broody hens, tried my incubator several times, but still nothing. To test out if it was just the hens and/or the incubator I purchased eggs, and they hatched out just fine. I tried cleaning some, and leaving them untouched, still nothing. Then I tried my duck eggs, and they hatched out well. What am I doing wrong?