THanks to the BYC website I have made me a homemade incubator out of a styrofoam cooler. I have had two batches of eggs in it. the first batch I hatch ONE... jsut one chick the second batch I got 4 out of it. My questions is ... I've candled my eggs and weeded out the unfertilzed eggs & such & even candled my eggs.. they appeard normal. when it comes to for them to hatch on this last batch I got 4 to hatch and three made baby chicks.. but never hatched. when I cracked the eggs open. the baby chick was there with some yellow yoke and look like some of the insides didn't develop or something.. What Am I doing wrong? Why are some hatching and the others make baby chicks just not hatch?