Have you done a
Overnight Chlorine Loss Test
I would also test the CYA again.
Also, you may want to try this method for reading your CYA as I find it easier and avoids staring at the dot as you pour.
Pour the mixed solution to a known level, say 90, peer in and confirm you can see black dot. Now pour mixed solution to 80 mark, peer in again, if you can still see dot, hold tube up and pour mixed solution to the 70 mark, then peer in again to view dot. Continue this until you are not able to see the dot - then use your CYA number as the value you last saw the dot. This method avoids constantly looking down the tube which can create the illusion of always seeing the dot due to staring down the tube. This also helps that you only report CYA values in decade numbers due to the logarithmic scale of the tube.