Throw some finely granulated dolomite lime into your soil, then your ph will be dead on throughout your grow no matter what ph your water is..
Simple as that![]()
The lime is a good idea, i use it myself. But, whether you use the lime or not, you still need to adjust everything to about 6.5 before pouring it in. Since your PH is a little high, it wouldn't hurt to water/feed with stuff PHed to around 6.0-6.2, but i wouldn't go any lower than that.
7.5 to 5.2 is a big jump in PH, and would likely shock the plant, so i'd recommend against it.