drain-to-waste ph

I am growing in 1/3 Ocean Farm, 1/3 peralite, and 1/3 coco using 2-Part Emerald Harvest nutrients with reverse osmosis water (my tap water is extremely 'hard' with chlorine and chloromine's). I water & feed drain to waste. I did a feeding in week 3 of flowering (day 55 from seed) and had a drain...