It seems you should be able to drag & drop the .blends to unity, so why export as an fbx, please?
Thank you.
You actually can drag and drop .blend files into Unity projects. But it's a trick I tell you! Heh Unity is actually pulling a fast one on you. Whenever you drag a .blend into Unity, behind the scenes Unity runs a .FBX export through Blender without you know. Seriously.
So while that can be a neat trick. When something goes wrong in the automatic export - and it does go wrong sometimes - it's frustrating not understanding what's going on. So by export .FBX manually out of Blender you're back in control of the process.