Eggs with no shell??

[4Crazychickens4me]

One of my hens is laying a eggs with no shell?? I had found maybe 4 or 5 in the past week? Not sure who is doing it though. They have oyster shells in their food already and are free range during the day. They all look healthy and are still eating and drinking regularly. It has been hot the past few days here but it did happen last week when it was cooler. Not sure if when they are out that maybe my rooster is making them stress or what. The rooster is in my new flock with 7 others girls that they are all out free ranging together. I still have them separated at night but plan to get them all together soon. Any help is greatly appreciated. Thanks

 

[chickens really]

How old are the Pullets/Hens?..Are they new layers?
Anything scaring them during the night in the Coop?

 

[sumi]

See #10 here for possible causes: https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/