I have an 18 month old black sex link hen that has been laying odd eggs for the last several months. The eggs are large and very thin shelled in areas, but not the entire egg is thin shelled. The shell is not smooth, but has ripples in it and a "sandy" texture. Parts of the egg are almost transparent. In all other ways, this hen appears to be healthy. My other hen's eggs are normal. These birds are in a large indoor/outdoor coop, fed layer crumbles, cracked corn, oyster shells and treats (veges, pasta, grass, hay, etc.). Any ideas as to what is causing this? Prior to this, her eggs were normal. Thanks!