So I'm finding I have to add a lot of bleach, more than double the PoolMath calculator recommends. For example, this morning I had 2.5 FC, I put 7.5 FC as a goal and added 130 ml. (assuming 2500 L). I tested 15 minutes later and only got 4.5 FC! Right now my CYA is about 35 or so. TC at 1. Is it because this bleach which says "concentrated" is just regular 6% stuff and not the 8.25%? What am I doing wrong?