Layer feed contains calcium in higher amounts than any other feed (grower, starter, all-flock, feather fixer, etc.). This extra calcium can be harmful to non-layers and build up in organs such as kidney, liver and heart, and over time can cause gout, organ failure and even death. Since almost every flock is a "mixed" flock, containing both laying and non-laying birds, many of us prefer not to use it (layer feed), but instead provide another type of feed and offer calcium separately. As
@rosemarythyme suggested, keeping a separate vessel of oyster shell works well because the laying hens will help themselves and all others will ignore it.
A caveat: you probably won't be able to tell that anyone is eating the OS. They don't need much and the level won't go down visibly, probably for several months. But they are. A five-pound bag could last you a year. Don't worry about it.