So they got the PH right but also depending on your plants age they should have a different range of PPM. At 2-3 weeks for clones it should be around 400-800 ppm. Could be slight nute burning OR lessened nutrient upkeep due to PH imbalance. Try watering when dry with a ph of 6.0-6.2. If you have coco your PH range can be anywhere from 5.5-6.8