It can cause one to pull their hair put if ya let it lol.
Easiest thing I can think of would be to test your tap water, your RO, the mixed water and the aged water of your tank. Odds are your tank should be zero. I suspect the mixed water should be dropping by now. And continue to monitor your tap and fresh RO for a while to pick up on any trends from your water supply or filters effectiveness.
I'm curious to hear results of the new kit.