I'm not Leslie but I'll chime in....your birds are fine on grit. Free range birds don't need grit offered as they can glean their own. You'd be surprised at what I find inside gizzards that has been used for grit~glass, quartz, cherry pits, stones, plastic BBs, etc. You're type of free range even has more offered grit than most, so no worries.
I know mine have gotten pain off the wellhouse that needs to be repainted, pieces of plastic that they've managed to find (the heavy kind of packing material), and probably some glass. Erg.