One of the girls lays very thin shelled eggs. She laid one today and before I could grab it up, she stepped in it. It broke and made a huge mess. Some readings online have told me to add 2 lbs oyster shell per 100 lbs feed. I do 50 lbs at a time, so I guess 1 lb extra shell? They have free choice of shell too. It also suggested adding vitamins to water while doing the oyster shell. What kind of vitamins and what's the ratio? Thanks so much, I'm afraid she needs a lot of help.