Hi Albert, I have the same problem and an "old cheese" on this site advised me to try acid titration method to assess the ph. This involves using a chemical - I was able to get Methyl Red - which changes colour when a certain ph range is reached. I don't have any experience with ph sticks. I want to try a swimming-pool tester kit which will offer a slight range of ph levels.
I wish there was a simple-to-operate ph tester that was also reasonably priced available for the hobby cheesemaker with a limited budget!
Good luck. I hope that some more knowlegable people on this site will respond to your (our) question.