How do I get rid of this weird light effect?

I’m turning my scene completely dark, I know I can tweak “Auto Exposure Brightness” to make it darker.
But how can I get rid of this white effect and make the materials look consistent?

That’s not the regular unreal editor?

Show normals. It looks to me like the edge is smoothed. Alternatively, you have a bad tangent basis and specular ends up stretching.

Turn up the roughness all the way and make sure the edge isn’t smoothed, like bridgedweller said.

Thanks. This is a custom map builder I’v created for my game.
The cube is not smoothed, This is a very simple cube with good normals that looks always good unless in this dark environment.

Thanks. Turning the roughness all the way up will prevent from the user to tweak the material’s properties like metal for example.