My wife got two chickens for her birthday from my mother and one of them lays white yolk eggs.
We got them when they were very young and the first few eggs were fine. We then went away for a few months, so we moved them to my sisters house as she has lots of chickens. My sister told me “Sakura” (the white yolk layer) was very much at the bottom of the pecking order amongst her chickens. Anyway we now have them back and so far all Sakura’s egg’s have had white yolks.
It would seem a bit odd if it’s down to her diet because we feed her egg laying pellets which are specifically to give the chickens everything they need to produce healthy eggs. And, our other chicken “Momo” lays perfectly normal, and if anything, really rich coloured eggs. They are both free ranged and they are both on the same diet yet Sakura’s are still white… :-S
I guess I’m in a perfect situation to do some dietary tests here.

Anyway, thought I’d share this with you all.
Thanks to John and coffee for posting this originally, at least I now know they are ok to eat as this is affecting half my batch. I guess we’ll soon know about longterm effects as we’re going to be eating lots of them by the looks of things. b