Texture displays dark on part of mesh

I’m importing floor models from blender into UE4. The texture of the red textured floor meshes display to dark. And one of the red floor part displays te right way.
The 3 parts are one mesh.
Only the visible part, the top of the floors are unwraped for texturing.
When rebuilding lighting there are no error messages.
But something is stil not right in displaying this mesh.

(See picture.)

Help please!

Thnx Lexa