Bypass the softener, sanitize the well storage tank and lines, and see if the smell continues. Your water test didnt test for Tannins which are common to an earthy smell. You may simply have some algae, or who knows what in your system. This is fairly normal and can be controlled easily if that is all it is. Have you done a thorough inspection of your well storgae/distribution system? The softener can also grow a lot of "stuff" inside, that is why I would recommend bypassing it during this testing to see if it is coming from the softener.
Let us know what you find.