I have a mix of old rescue hens and young pullets (mostly not laying) 24 girls and I average 3 good shelled eggs a day. The problem is about every 5 days someone is laying 1 that looks like a snake egg. the first had a thin membrane around it, the second was leathery, and the last one kinda crinkled like dry leaves. I don't know who is doing it but I'm guessing 1 of the old girls (they were in bad shape when I got them a month or so ago). My question is will it stop with good feed? I feed a 50/50 mix of 16% layer crumble/ feather fine with daily fresh vegis, scratch grains, and I've been mixing in crushed egg shells for calcium. They also can get to the ducks 18% meat bird pellet but most don't seem to like it.The old ladies "look" great now but this makes me worry they won't recover from their previous life. Any advise on the thin shelled eggs?