I think the first clue in the post was the admission of having plenty of double yolkers in the past 3 years. I've been raising flocks of 10-50 chickens since I was 10 years old and can count on one hand the number of chickens who laid double yolk eggs...and that was dealing with production breeds such as RIR and WLHs for the first few decades.
Having that many birds with abnormal ovulation is indicative of something and it can't be a good thing...abnormal is abnormal. Overfeeding, increased soy proteins, keeping chickens until they are old, breeds prone to obesity and abnormal ovulation, etc. can yield abnormal egg production, reproductive cancers, abnormal shell production, etc.
The occasional weird egg is a given but having many, many occasions of abnormal laying in a short period of time would indicate a flock management problem or possibly something wrong with the water/environment. Time to change flock management, breed or where you live when you start getting abnormal laying that frequently.
Having that many birds with abnormal ovulation is indicative of something and it can't be a good thing...abnormal is abnormal. Overfeeding, increased soy proteins, keeping chickens until they are old, breeds prone to obesity and abnormal ovulation, etc. can yield abnormal egg production, reproductive cancers, abnormal shell production, etc.
The occasional weird egg is a given but having many, many occasions of abnormal laying in a short period of time would indicate a flock management problem or possibly something wrong with the water/environment. Time to change flock management, breed or where you live when you start getting abnormal laying that frequently.