Have you ever seen sneezing in your flock? This is a good link to see what the possible causes of wrinkled or body checked eggs:
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/
A defective shell gland in the oviduct can sometimes cause those.
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/
A defective shell gland in the oviduct can sometimes cause those.