This is exactly my thoughts. The Organic feed used by the OP and the "Scratch and Peck" feed used by
@Michael Propst are both non micronized which means that they have quite large fragments of grains enabling a chicken to pick and choose between ingredients and meaning that if a particular chicken has a taste for one component of the feed, they will actively select them over others.
I think it is
very relevant that both hens that were diagnosed with this fatal disorder were fed a course mix feed like this and sadly at great expense to their owners who thought they were giving them the best they could buy.
I posted on your other thread about my views on this necropsy result but assumed you were feeding scratch. I would encourage you to change to a micronized feed.... probably pelleted is best. Chickens can pick up tiny specks of things you can barely see, so it is not unreasonable that they will pick their favourite bits out of a feed where the particle size is this large...... in my opinion the feed is the problem, particularly if it is fed from a dispenser where they can clearly see all the particles or even scattered on the ground. I imagine there may be some considerable waste when feeding this product as there will be a strong temptation to all chickens to bill out and eat only their favourite bits.