Pool is clear, ph dropped to 7.2 from 7.6, ta 90 cya is 40 , put in 16 ppm chlorine to 1.5 already in last night to shock pool. and added 45 lbs of calcium chloride to increase ch. what has caused the fc to drop to 0 and ph to drop to 7.2? I did have several swimmers today! Going to add 2.75...