I have 14 layinghems, mixed breeds : golden laced wyandotte, Russian orloff, jersey giant, well summer and true blues. My two true blues have thin shells compared to anyone else and their two daughters, orloff roo, have thinner shells as well. Not as thin as the pure bred mommas but thinner than the others. All get oyster shell freely and crushed egg shells as well.... what else can I do? The two mommas are about two years old and the daughters just started laying in dec. They are thin enough that just setting them gently in an egg basket breaks them or if another hen lays in the Same box they will break. Any ideas?