My dad recently started raising chickens. He had great luck with his eggs at first, but more recently, some of his eggs are getting stress cracks at the end. I didn't think to take a picture while I was there yesterday, but it looks like the egg is thinning in spots and there are small cracks coming through the membrane, but not the actual shell. Most of the cracks, which we've called stress crack, are on the pointed end or small ones along the side. It is not every egg, but a large majority of the eggs. He is feeding the same feed that he started with, and supplements with oyster shell for calcium. Has anyone experienced this before and have tips to share? It would be much appreciated! Thanks!