one of my 6 hens i have been raising layed her first egg this am. i found it on the floor of the coop in the straw. It was paper thin. When i picked it up, it caved in all over. Question: is this normal for a hen's first egg or do i need to add oyster shells to diet? FYI: this hen eats the same layer crubles as my other hens and their eggs are hard as a rock. I feed them laying crumbles and they free range also.