I appreciate your reply, but my concern in the initial post was that the TDS was too *low*, at only 105 or so (when sources say 150 is the lowest ideal TDS). However, according to other messages elsewhere I've learned the TDS isn't as big a deal as I thought? I still wish I knew what was going on.
If you don't mind me asking, how recently have you checked your TDS? If you're afraid that your TDS is too low, you can get something like SaltyShrimp GH+
. Your KH, at that level, should not be a problem.