Salt, salt, salt, salt. Check that salinity. Get a hydrometer, or take a sample back to the LFS, and have them test for salinity. I bet it is way too high.
If you can somehow get water from before your water softener, I would use that water, and start doing water changes now.
Also, check your softener unit and see if it has a bypass, or call culligan, and tell them that you need a bypass put on, for your FRESHWATER aquarium.
Reading this thread from the beginning, I am almost positive that this could be the root problem.