Hopefully you're feeding them some type of layer feed or all flock. Especially if the latter, but regardless, I'd get a bag of oyster shell and set out a feeder or dish for them. If they need it, they'll eat it, but won't if they don't.
You'll also need a place for them to lay eggs. If you don't have nest boxes where they sleep, just a short open box a little bigger than they are with some straw in it would work. You'd only need one for all three, not one for each.
I hope you're getting some eggs soon! That's eggciting!