Hen is laying different size eggs?

[hogfan]

Our hen Bok Bok is in a tractor by herself so I know these both came from her. Why is she laying two different sizes? The large one (her normal size egg) won't fit in an xl egg carton and the small one almost looks like a bantam laid it. Is it a nutrition problem?

 

[PattiS72]

Some of mine do that. Sometimes it is a double yoker. I also have gotten some really tiny ones.

 

[sweetbeak]

I have two hens that do that all the time, they lay every second day and the big one is always a double yoker