I have a hen that has trouble occasionally with egg shell quality. The soft shelled eggs and shell less eggs are very fragile and will break easily. The flock will eat the contents if they find it, leaving only the membrane behind. My hen laid 2 eggs from her roost last night, one was a soft shell that broke on impact and the other one was normal. Today, she gets to have a human calcium citrate tablet (generic Citracal) to give her a calcium boost. She'll get 1 tab a day until her Shells are nice and normal. She doesn't like it, but I wouldn't like her to have an egg break inside of her and be fatal, so she gets the tablet. She's not a fan of Oyster shell but she will eat egg Shells occasionally. I've tried her on an all flock feed and a layer feed and I don't see a huge difference in her egg shell quality. Right now, I'm trying a new brand of layer feed. We've had some really hot days and I feel like that's messing with her, plus I needed to round them up quickly and offered scratch to herd them in. The scratch more than likely played a significant role, but its not a normal thing at all. I only buy scratch to feed the 20+ wild Canada Geese that visit me to eat and I couldn't afford to continue feeding them my ducks feed, so now I have scratch for them and used it as a last resort for herding my hens. Some hens just require more calcium than others. As long as you're not giving a calcium boost to all of them and only do it whenever it's necessary, I feel like it's perfectly acceptable and far better than the possible alternative. I'd stop treats. My girls get a bowl of mash (their feed made mushy with water) every night and they LOVE it. That's their treat. They've come to expect it now