Our Orp is laying eggs with paper thin shells. Worse - she decided a month ago that she likes laying off the roost in the morning so now we are lucky to get one intact egg out of her a week. The problem is our other birds' shell quality is fine. They are all offered oyster shells but rarely touch it. I just started adding it to their scratch treat in the afternoon but I've read that too much calcium could cause health issues. Is this a real cause for concern? I can isolate the Orp to feed if absolutely necessary but would prefer to skip this if I could. Any guidelines on how much and how often I should sneak extra calcium in the scratch? How long should I wait for shell quality to improve before I increase the calcium amount?