It sounds like they have a wide choice of eats, I would still offer oyster shell free choice as well.
Hopefully it's just a 1 time glitch - here's an article that may help you
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/
Hopefully it's just a 1 time glitch - here's an article that may help you
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/