sport marans:

[NatJ]

My Marans eggs are a 4, maybe, but still a lot darker than my hens eggs with dominant white, so no chance of mix up there.

Good to have that checked!

I think it's either dominant white rooster's long living sperm

I think that is probably it, considering that it makes more sense than anything else that anyone has yet thought of.

or it could be possible that there is a co dominance between white and black. The hen could have one normal dominant white gene and be mostly black, because maybe her dominant black gene is a very strong phenotype/variant. This over powering dominant black variant was passed on to only half of the chicks and the same with the normal dominant white gene. Meaning if I understand it correctly 50% of her chicks could be white?

I have never heard of Dominant White behaving that way. What you describe does sound like a way in which some gene could behave, except that it is definitely NOT the normal behavior of the genes involved. So it would be very unexpected.

If you continue to keep this hen separate from all the males with Dominant White, you could see if she keeps producing chicks like this (which means it is caused by something in the genes of herself or the roosters you want her with), or if the mostly-white chicks quit happening (which would be a strong indicator that the ones in this batch were sired by long-stored sperm from a Dominant White rooster.)

Don't think its silver, based on the fact that it effected both male and female chicks, even seen in the pic posted above.

The one we know for sure has silver is the male who is mostly dark-colored but has some silver on his head and neck.

I think the mostly-white ones are probably not silver, but since I knew that at least one chick did have silver, I was trying to make sure we had good reasons to rule it out as the cause of the other chicks.