I set 17 eggs in the incubator 8 days ago and I candled them tonight. The eggs weren't fertile except 1. The eggs were saved for 7 days before incubating. I had dewormed my chickens a day or two before starting to save them. I used wazine. I know that my rooster is several years old but if he is not fertile then I would not have got the 1 fertile egg. So my question is,is there a chance that the wormer caused the infertility in the 16 other eggs? I also thought that his count may be low because of his age. So how old is too old?