Going on week 3 with water in the new pool. Chlorine seems to drop overnight, from 3ppm to 1.5ppm, is this a normal drop? Also bought bleach at Home Depot, it's their brand, Germicidal Bleach, but I can't tell if its 8.25% or 10% strength. Using pool math, if it's 8.25%, it suggest to add 32...