When I opened my pool this year the CYA was undetectable with my K-2006. This was not surprising since I keep it low and the pool level was dropped substantially over the winter. So, I added 24 oz of CYA I had left over from last year. After a week there was no change in the reading. Iíve since added another 36 oz over the course of the past few weeks. It just now registers barely 20 ppm. My CYA reagent and the 36 oz of CYA were purchased this year. PoolMath indicates the amount of CYA Iíve added should bring it from 0 to 40 ppm. I thought CYA had a shelf life of at least a couple of years if stored properly which it has. What do you think is happening here?