Hi! I have 9 ex-batt girls and recently we've been getting the odd rotten egg. They are fresh, no obviously damage to the shell but are completely black inside and the smell is possibly the worst thing I've ever come across. All hens seem ok (apart from one who is broody at the moment) but I am guessing one might have an infection. But we get 8 eggs a day, which I assume is from each chicken not including the broody one. But we maybe get one rotten egg a week. Surely if she had a bad infection every egg she laid would be like that? Does anyone have any other ideas of what might be causing this, and practical ideas of how to isolate the hen laying these?