I purchased a pop up pool for my kid to start swimming in. 12 feet x 30 in deep. Wall skimmer with a filter pump. New to all of this but so far ph is 7.2 to 7.5 alkalinity 80 to 120, hardness 200, cya 30-50. Here is my problem/ question at night I do my chlorine 2/4 to 3/6 is what I get on hth 6 way test strip. Morning I test 2/4 by mid day fc is back to 0/0 what am I doing wrong or is this ok???