You could offer them crushed eggshells.
If you add water to chicken food to make a mush, chickens usually think it's a treat. If you mix oyster shell and chicken food, then add water, the chickens might eat the oyster shell along with the chicken food.
You could sprinkle a little oyster shell...
Yes, it does.
That scratch has 15% protein.
Recommended protein level for laying hens is 15%-20%, depending on what source you consult.
It's certainly got more protein than many other kinds of scratch grains, but I would not call it "full of protein."
It's got less than half a percent...
Scratch is a mixture of grains--usually cracked corn plus whole oats or barley or wheat or a mixture. It's a fine source of calories, but does not have enough protein or the right balance of other nutrients to be a complete chicken feed.
It's called "scratch" because it usually gets sprinkled...
I agree it sounds like they are not eating enough oyster shell.
When you eat eggs, do you give the shells back to the hens to eat?
If you do not, you might try it--the shells of their own eggs will not be enough total calcium, but might help a little.
If you do feed eggshells and they eat them...