Blender to Unreal - Normal of Materials issue!

Hello everyone! im just starting to play around with the engine and it looks very promising all what I could do with it. But because I’m a noob at the time im not very familiar with some concepts:

Im creating a static mesh in blender and managed to separate some parts of it so I can apply the desired materials later with Unreal (materials are created in UE4). The problem is that once that I imported the mesh to unreal it works just fine, except for the fact that it seems the normals of my materials just dont work on that mesh, in other objects the materials works fine (eg: blueprints and other imported meshes), am I doing something wrong? the scale is the problem?

Please help!

flip the green channel on texture settings?