Need help or advice

Some of my hens or my rooster have started eating my eggs. I feed them laying crumbles with oyster shell mixed in. I have 10 hens and I'm getting like 5 to 7 eggs a day and most days I find two eatin. The shells are a lot thinner than they have been. What's makin them thin if I'm feed oyster shell. I have three nesting boxs and still find about two eggs a day on the ground. I got golf balls in the box. Need help to stop this bc I'm selling the eggs for hatching and don't want then eating them.