Maya models and lightmapping issue

I use Maya to model all my game assets, however when ever I extrude a polygon shape, that extruded part gets lightmapped a darker shade than the rest of the model in Unity. I currently am exporting as .FBX with default settings. Any suggestions?

You will most likely either need to apply (Map) some UV’s in Maya after your modeling (extruding) is complete preferably on both channels (which you will need for any texture mapping anyway) or check ‘generate lightmap UVs’ in the Model Tab in the inspector for your imported FBX for Unity to generate the second UV channel for you