I'm no scientist, but I don't believe a soil-less medium changes the PH of the water you add to it. When I first started I would check the run-off from the pot and it was always very close to the PH of the water I added, so never checked again. If I even suspect a nutrient lock, I just give it plain PH adjusted filtered water, and it clears it up right away. Even in flowering I never give the plant more than 2 nutrient feedings in a row, so I never have the salts build up.
Bottom line, I never worry about my medium after the pots are filled. And I used to grow 100 plants at a time in California.