They are eating Nutrena Egg Producer ( https://www.nutrenaworld.com/product/country-feeds-egg-producer#guaranteed-analysis-anchor ) and free range (heavily supervised) on pasture land 4 days a week. At my breakfast, yolks are nice and dark yellow, and delicious! No added supplements.What is their nutrition like? Are you supplementing with vitamins leading up to and during egg collection?
I've hatched many EE chicks near 100% making it to hatch with the exception of one hen that this cock hated and her eggs were never fertile. Interesting to note, it was a Gold Sexlink and another hen I had to rehome was a Buff Orp. that he also attacked. The Wheaten girls are in that gold color category... And my black colored layers are ragged from "use". I'm getting rid of my layers soon and will only have the Wheatens. If he doesn't spread his love around after the layers are gone he's going to go too. I don't have patience or space for a finicky cock. Right now he is in an area by himself so another cock can have a turn. Maybe this timeout will do him good.
The eggs just went on lock down and the 2 remaining Am. eggs have movement and the OE eggs are moving as well.