Yes, Oyster shell calcium is preferred but sometimes a hen will not eat it. If so, adding a tablespoon of DE in the feed will correct soft shells in a day. After that, going back to calcium is a good idea.
Sometimes chickens are just silly!
True that..and are you the one that mentioned the Calf Manna? I love it. I use it sparingly in the spring and summer when they are free ranging, but I give it to them a bit more during the winter when they aren't free ranging. Love the stuff.