I have a pentair cya test kit (R151226 79) and getting quite a significant difference between different reagent bottles. I was using one that was almost empty and got a result of 120ppm. Tested in exact same lighting conditions. Used a bottle that’s never been opened and got 60ppm. There are no expiration dates for these so I’m not really sure what the deal is. Got both reagents no more than a few months ago. Could one just be a dud? Not sure what is actually correct. I can’t be having variations like that since this is a commercial pool. Any more accurate testing for CYA out there? Thanks.