Hatching mysteries

the only thing IMO u can do is like you said go by candling the eggs. determine if you can how far along they are by candling and then go from there for lockdown. you think a hen would know what eggs need to be turned and what eggs need to be still for 3 days? shed lay a clutch and go by the 21 days then. staggard hatches are just not a good thing to deal with.

 

I don't know if you have a turner then you don't have to worry about turning the eggs. If you don;t have a turner then I would turn them around 7 am, 3pm and 11pm. Apparently the person you got the eggs from was hand turning them that is why there is an X on one side of the eggs and an O on the other side of the eggs. Always turn the eggs in the same direction so that at 7am all of the X's are up, at 3pm the O's are up and 11pm the X's are up. Then the opposite the next day. Just my opinion.

Here are a couple of pictures a friend of mine took to illustrate.


Here is a thread with egg candling progression pictures. You may be able to tell approximately how far along the eggs are.
https://www.backyardchickens.com/forum/viewtopic.php?id=261876

 

I would think you would just have to keep turning until you can either see with candling they are ready or you know by the date you put them in the bator.

 

I had a similar situation with guinea eggs I "liberated" from the hen's nest (since guineas are notoriously poor mothers). I candled until the air cell looked about right and the rest of the egg was uniformly dark (the only visible movement was along the air cell line). I put them into lockdown at that point, and sure enough, they hatched two days later. If you can set up a hatcher out of an old cooler or something, you could use this approach to move the eggs to the hatcher in batches. Even if you have to set up the hatcher as a still air, that would be better than trying to do a split hatch with only the bator.