CBD Auto Cheese

Another rainy week. Watered on 2 different days with a total of 14 liter nutrient solution this week. Before watering I tested soil PH under this plant and got a reading of PH 7. After watering with 7 liters that contained 5 ml of PH down and waiting a few minutes, I got a reading of 6.3. Before watering the PH of the soil under the plants was 7. Today's watering with a 7 liter container which had 5 ml of PH down the plants came up varying amounts of PH levels. Plant 1 (the oldest) had PH 6.6; Plant 2 had PH 6.1 and Plant 3 PH 6.2. It would seem that my soil has an inclination to revert to a PH of 7.