There is a possibility that various other factors could alter the pH of the shampoo?, so lowering the pH could be tricky at times. First, make sure that the pH strips are working correctly; test them first with lemon juice, and the pH strip colour should be closer to the acidic side, which is approximately 2.3. Additionally, be sure your water's pH is neutral since sometimes that might not be the case. If these two conditions are met and you are still experiencing problems, make sure to check if all the other ingredients are pure or not, as sometimes they contain additives. You can even add more lemon juice to balance the pH, which won't cause any problems as we are making it close to the scalp pH.