What can cause this shape in egg?

[Pay-fy]

I rescued 3 hens while back. After going through a sickness and pests (at least I think the pests are gone) they started laying for 2 months. 2 weeks ago one of them stopped laying and she’s acting normal didn’t lose any feathers and doesn’t look sick. Another one laid this egg today. I feed them layer feed and grain mix feed. They get 2-4 hours of free range because of predators. I also left oyster shell on the side. What do I need to check and what can cause this?

 

[GodLovesU]

I think this article may have some information on this:
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/