Hello, I grow in amended coco coir, 60% coco coir 40% hydroton. I use the heads formula General Hydroponics 6/9 micro/bloom per gal water. I currently water 3 times per day, automated system. First irrigation is 20 min after lights on, second is 4 hours after lights on, 3rd is 8 hours after lights on approximately 20% runoff My starting tap water ranges from 0 PPM to 50 PPM on a Blue Lab meter. I have seen this problem many times in the past and I do not know how to fix it. This specific problem seems to happen after about day 30 of bloom. This particular run I am at day 31 and I just took 3 seperate runoff readings and these were the results: Input pH / ppm = 6.0pH / 650 PPM / 1.3 EC Cultivar A - 5.0 pH 650 ppm Cultivar B - 5.3 pH 700 ppm Cultivar C - 5.4 pH 680 ppm What typically happens when I have this problem is the ph will continue to fall into the high 4 range, the plants will stop growing, the hairs will turn brown, natural oils / smells will die off and lose their odor. some advice I have seen in the past has been: Use calcium carbonate to buffer the water (I dont know how to do this?) Use citric acid and then potassium hydroxide in concert and quicky feed to the plants to re-establish the lost buffer Pre-buffer the starting water before adding nutrients via calmag or ph up to approximately 100-150 ppm What I would like to know if anyone has seen this problem before or has corrected it and any suggestions. Thank you in advance!