I have 6 Hens 3 each, RIR and BR. One rooster which is a Cochin. They are all good layers. The problem is I set 41 eggs in the bator collected over a week. When I candled them on the 8th day Out of the 41, only 6 were fertile with movement. The rest were all clear. I opened several up and they were just yolks and whites. Is this normal to have so few that were fertile? Or is there to many hens for my little rooster??