You are on target-I would make a slurry of RO/distilled and as much soil as you can and still have a slurry, and not a soft clay.
I suspect I had an alkaline increase with daily watering with 7.6pH water and all the rain we had this year, which is at least 7.6pH here. I used some MirAcid twice, and saw some improvement. I have no tester at this time.
