Until a pullet (young hen) gets into a rhythm of laying eggs, she will lay some oddities. I've had some with no yolk, they are usually smaller. In a couple of weeks, the pullets will calm down and lay nice normal eggs. Younger chickens lay smaller eggs, and older ones lay larger eggs. But that is not to say that a young pullet will lay a very large double yolked egg. Did you cook it, sunny side up, and serve it?