Fake stones are difficult to get right. Perhaps using a 'tex coords from xyz' before the stones will help, but it may also mess up the texture space. Sometimes when using more texture PF's I add one of those between the PF's, to get the smallest texture alright, but it is a matter of fiddling.
Or use real stones as a pop?
Or make the stones by displacing up small stonebases from a voronoi, then a compute terrain/normal very small scale, followed by another displacement by normal (or a mix of normal and lateral), masked by the original voronoi white, so you get smoother stones.
