Clutch hatching on different days?

[Headgear]

I have a clutch of Black Copper Marans eggs hatching. Out of 14, 8 hatched on day 21 (yesterday) with two more pipped as of last night. I haven't looked yet today but I would bet that one or two of the remaining unpipped eggs have gotten started last night. I bought these eggs from lady here locally. She said that they were all collected over a four or five day period and they were all set at the same time. What causes some of them to hatch later than the others?

FYI, I had a them in a new Genesis Hova-Bator, with an automatic turner till day 19. The humidity was +/- 45% and the temperature stayed very constant at 99.8 At day 19 I put them in another Genesis without the turner to hatch and raised the humidity to 65% and again the temperature was very steady. Any ideas?

Thanks

 

[Double Laced]

One of the things that causes this is when eggs are left in the nest for a few days rather than being collected, they are sat on and kept warm while hens lay new eggs in the same clutch / or / all you need is 1 or two birds that sleep in a nest box and incubation can start on a few eggs for a day or two before they are collected.

Also with some breeds is is not unusual for a hatch to last two or three days, happens a lot with my barnevelders. When i raise hybrids they all seem to hatch within a few hours of each other.

Do you use a incubator with a fan, Hot and or cold spots can develop leading to a sporadic hatch.

 

[Headgear]

Yes the Genesis has a fan and I put all of the eggs in the center just to be sure. The lady I got the eggs from said that see collected them eggs twice a day but I noticed that she had them in her garage and the temperatures here were running in the mid to high 80's. I think I would have kept them in the basement where it was cooler and more stable.

Eight of the 14 hatched, two died when they were halfway pipped and I haven't opened the others yet to see what happened with them.

Thanks