I'm a back yard breeder, mostly for fun with my young girls and to sell locally. I have been breeding for the last two years. RIR roo to RIR hens, barred rock hens, easter egger hens, and black star hens. In past two years, I have only bred in early spring through late summer and typically get between 85%-90% hatch rate. This late summer I switched to an amauracana roo. The last 3 attempts at hatching I'm 5/42 all three times. I've candled and everything looks fine up to 17/18 days but then they don't hatch. I've opened up dead eggs and everything appears to be fine with respect to development up to where they just seem to stop. I monitor temp very closely, I don't monitor humidity at all. When there is no more water, I add some to the pan. During the summer it is really humid and I only refil water once over the 3 week period. Now with it being more dry, every 3 days. I know people will want to say that my problem is my not paying attention to humidity, and that may be right, but keep in mind I have 20+ hatchlings under my belt with between 85%-90% hatch rate using my "method". The only changes is a new roo and change in temp. I don't understand why everything is fine up to 17/18 days and then almost everything dies at that point. Any thoughts or suggestions are most welcome.