I have 40 eggs in the incubator today I candled them all and 6 have formed an embryo but the embryo died and made a blood ring and black clot looking spot. what causes the embryo just to randomly die they died at about a week into development. I have been keeping my temp right on at 99.9 degree and about 55-60% humidity and I roll them twice a day. I lost 10 eggs total because 4 were infertile on top of the 6 that died and I have 4 or 5 more that look questionable but I left those in the incubator. they are due oct 15th what can I do in future hatches to prevent so many from dieing?