Any out of context materials found around a camp site were brought there for possible use. Many times while digging a "very nice" grinding stone ( mano ) will be found but have zero evidence of being used.
The bottom stone in the pic looks in that catagory, just natural textured surface, brought home but never used. The beveled top right seems a good possibility of being actually used as a grind stone.
If they are indeed sandstone manos from your area, they are a classic example of the type of material that
eventually also ground down teeth