Edges/Seams/Shadows ugly with Mobile/Diffuse shader

Hi,

After creating a model of the wall with windows in Blender and importing in as fbx into Unity 5, baking the lighting in a scene with multiple point lights the result is rather ugly with edges/seams darkened like in the image attached.

The texture is a simple 1024x1024 uniform colour image. The shader is Mobile/Diffuse

I tried setting Normals to "Calculate" and increasing the smoothing angle in import settings.

This is what it is supposed to look like (rendered in Blender) - a simple painted wall with a window:

What could be the problem causing these these dark "mouldy" patches along the edges in Unity?