Why is this egg small

[Buddyfarm11]

I was out collecting eggs today and then I saw a very small suspicious egg it is light brown bantam sized but none of my banties lay this color they will either lay white or brown but not this kind of brown here are the breeds I have that are laying:
Dark Brahma
Black/Barred Cochin
White Leghorn
Japanese Bantams
Here is a pIcture of the egg

gas you can see in this picture I compared it to a cochin egg and it looks way too small

It is so small could one of my girls layed it?

 

[brahmabreeder]

It could be a fart egg or one of the bantams just layed a small egg

 

[Buddyfarm11]

It could be a fart egg or one of the bantams just layed a small egg

Maybe a fart egg cause I keep the bantams apart in a different cage and the egg was inside their nesting boxes but if its a fart egg should I be worried?

 

[brahmabreeder]

I don't believe so. I think they are just eggs that went through the hen a bit too fast so they didn't have time to fully develop.