Plants not growing and minor/medium algae problems - lots of details

[MagooWu]

GH/KH Test Results are In:

Well:
15 kH
15 gH

Post-Softener:
15 kH
11 gH

Current Tank Water (Was all Post-Softener):
15 kH
7 gH

So - does this assist in determining if I should use well water, softened water?
Any additional steps to take with the water pre-water change?

Any help would be appreciated.