Over half of the eggs that my 2-year-old Cochin has laid in the past couple of months have an incredibly thin shell on one tip that usually ends up broken or cracked before I can even get it out of the nesting box. I haven't had this problem with my other chickens and I have been giving them yogurt periodically since it has started for extra calcium. She does lay oddly long eggs, but that has been the case since she began laying. Is this a medical symptom that I should be worried about, does she need more calcium even though this habit is limited to her? The rest of her eggs are quite solid. Any advice would be appreciated.