Vertex painting material differs from actual material.

Hi currently I’m working on a environment in ue4. now I want to use vertex painting to blend my wall mesh with the floor to hide the hard edges. but I have set up the same material painting texture that i use on my wall as well but the colors of the texture on my floor are different than on my wall.
while I use the same diffuse,normal and specular map for both materials.

my floor material is set up to blend the textures based on the height map of my bricks on the floor so that the sand fills the cracks first and afterwards the rest. I paint with the red channel.
what causes this or how can I make it so that both materials look the same ?