When you grow organic pH should be 6.5 or more, stripes are not useful. In your pot live bacteria and low pH will kill the in some parts. They are helpful for your roots. I think you should give them only water without nutrients and do this every week. Once with nutrients and next time without...
By adding correct amount of nutrients like you said A and B to get correct reading.
I used word correct because it's all based on your water. Hard water high eC soft low with this knowledge you easily can adjust correct amount of nutrients to your water.
An electrical conductivity meter (EC meter) measures the electrical conductivity in a solution. It has multiple applications in research and engineering, with common usage in hydroponics, aquaculture, aquaponics, and freshwater systems to monitor the amount of nutrients, salts or impurities in...