Like SonKim wrote you need to disable SRGB in the texture options within UE4 and you need to this for all your exported black and white textures from SP or SD like Metall and Roughness.
Like SonKim wrote you need to disable SRGB in the texture options within UE4 and you need to this for all your exported black and white textures from SP or SD like Metall and Roughness.