Update: There's nothing problematic to report. I'm running the column at +/- 200ppm (measured electronically), far less than the recommended concentration. Eveything's is as it was except water seems slightly clearer, but that could be attributable to the 2x40g WCs during this period. Anecdotally my fish seem a bit brighter. I have one fish that will let me touch him now and then, he feels nice and slimey.
BTW, in order to manage SG I have a a supply of concentrated brine that makes the process much easier.