I am having this issue with my 5 young Red Production Layers. They are 20 weeks old and the first egg was laid one week ago. I've had a triple yolker, double yolks, and two without a shell. Another had a shell so thin it was punctured upon laying. I was feeding them development feed until now and realized it had only a fraction of the calcium that the layer feed has. I should have started them on the laying pellets two weeks ago. I am hoping that the introduction of the layer pellets will help with getting enough calcium to the shell. I feel badly for not having the right feed at the right time.
I have read that it is not uncommon to have some irregular eggs when the hens are just starting out.
I've also found a couple of eggs just dropped from the perch... taken by surprise, I'm guessing!