Yesterday I had chicks hatching out. I had about 22 in the incubator. I had sponges filled with water, troughs all filled and the humidity was between 85 at the best and 78 at the worst. The vent was open. 15 chicks hatched out perfectly. Then 5 stuck. I NEVER opened the incubator either, but I could see that a few had pipped and then got stuck. I just don't understand why? Has this happened to you?