Strange laying

Last night when the chickens were going in for the night, one of the pullets outside the pen dropped an egg with the shell so thin it broke. All I saw as just a fluid and the shell on the ground. For two weeks now 2 of the pullets have been laying eggs about the size of quail eggs. These are BO and Wyandotte crosses. Every morning for the last three I've had an small egg dropped overnight. It didn't bust but there is no shell. Just the membrane and the insides. Once, 4 days ago, on top of the poop from overnight, was just an egg yellow. The older girls I have never went through this. They just started laying. Not at 16 weeks for sure. They did wait till 22 weeks.

Does anybody know what's going on with the pullets? If they were born with just so many, they sure are wasting some.