How did you measure the soil pH? Was it one of those $10 two-prong meters? (They're not too accurate/reliable. I have a $70 Control Wizard Accurate 8 soil probe and it's fairly reliable. Unnecessary, but nice to have when you're curious, testing a new bag of soil, etc.).
There is
a runoff method, but it's tedious and time-consuming. You would need a pH pen (strips probably won't work because the liquid won't be clear). You can get an eTechCity PH pen on Amazon for about $25. Depending on the seller it will come with a foil pack which you mix into distilled water to make calibration solution. If you have the money, that can be fun to play with. But, they're kind of a maintenance headach and ongoing expense (you have to have storage and cleaning solutions). I have two and stopped using them a long time ago.
A ppm meter is a better $25 investment. You can know the ppms of your water (which can make a difference), and your nutrient mix, but especially your runoff. That's handy to monitor. I find runoff ppm is a better indicator of soil acidity. (I.e., salt buildup.). For me, if my runoff hits 2000ppm, I do half-strength nutes and increase the runoff. 2200 is the danger zone. 2500 is where it starts showing in the plant.
Your numbers may be different. But, it's very handy to know those numbers when dialing in a soil and nutrient. (If using a soil with nutrients "cooked" into it, it might not be as useful.).
