I usually measure the pH when the milk is close to the temp I want for ripening, then add the starter. The only time I have seen it go up, the pH meter needed cleaning from the fat in the milk. So I swished it in warm soapy water, rinsed it well, patted dry and re-checked against my calibration solutions. Then rechecking the ripened milk it was as expected to be, a little lower than my initial pre-ripening measurement.