Landscape materials - shiny edge between matt materials/layers

Hello

I just noticed problem, before I work on landscape layer materials with non 1 roughness. Now I have pebbles, they are set for test roughness 1, means - no glossy. Field grass is test material with same roughness 1.

Problem is on edge between this two materials - is glossy - on screen you can see brighter material, but this is shiny/glossy, for sure not roughness 1 and in game it looks much worse than on screen. I tried few changes but any improvements - please help! :wink:

Thank you ++