Using the TF-100 kit w/ R-870/R-871 components. I balanced the pH and shocked the living daylights out of the pool with liquid chlorine. Went to test FC. Put scoop of R870 into 10ml water with speedstir, turns clear right away. A second scoop it stays pink. Then 70 drops of R871 tells me I am at the correct shock level for CYA of 90. Am I doing this correctly?