I guess so. I was testing the FC and CC with my TFT test kit, and after 2 drops of the first reagent, I realized I had forgot to add the powder. So I added in one spoonful, then continued with the drops...3,4,5...I only got to 9, FC 4,5 when it went clear, I was expecting FC 7-9. Ok, strange, but not terrible until I counted off CC drops all the way to 4,0! I have never seen 1,0 CC, so I knew something was wrong, or maybe my kids had peed in the pool 2 hrs earlier, well that would be wrong too. Anyhow, I tested an hr later, thinking maybe adding the powder to the 10ml pool sample plus 2 drops would change the reading. Sure enough, I measured FC 8,5 and CC 0,5.
I'm curious whats going on with the chemistry there.