I have some silkie eggs in an incubator. I marked them with the dates they were laid. 9/8, 9/13, and 9/16. I thought the one from 9/8 should have hatched on 9/29. It did not hatch yet. I did the float test today and it passed with about 10% floating. Does the 21 start from the day the egg is laid or the day you first see the veins start to develope? How long should I wait?