This is only my second summer/winter with chickens. This last winter I added 4 NHR hens to my flock just as winter was kicking off. From the start I was getting at least 1 double yolk egg every week from the new girls. I was also getting the odd "no yolk" eggs, and very frequent wrinkled/thin/deformed eggs. At the start of spring I lost one of the NHR girls to internal laying. After she died I didn't get anymore mutant eggs. I chalked it up to a genetic defect or something- they must've all been from her! Well, that same winter I had started feeding my girls layer feed every day and gave them a seed block since the ground was caked in 8" of frozen snow. They are normally free ranging on acreage and eating kitchen scraps- I don't usually give any grains. Didn't think anything of it. Once spring hit, the grain stopped (same time as my hen died) and it was back to free-ranging. I had ZERO double yolk eggs last summer, and ZERO this summer. Both summers were grain-free. Now it's cooling down again and I'm back to tossing grain out once a day. Suddenly I've gotten 2 double-yolk eggs between 3 NHR hens (the only ones that lay brown in my flock) in the last month since starting the grain again. I've also gotten several wrinkly and deformed eggs from them since starting grains again. Has anyone else noticed a corrilation with this? I'm just feeding 16% layer feed from D&B, but saving up to switch to non-GMO feed.