I have 12 eggs in our incubator they are chocolate bantam orpingtons. They have developed normally and then stopped. Only two are still developing it is the 15th day and those two have filled the entire shell when we candle and the other ones are still black clumps on one side of the egg and we cant see them moving when we candled as we could before. I have read places bantams and orpingtons are harder to hatch is this true? Any suggestions for future hatchings?