Flush your plant at 3X pot size ( 5 gal container equals 15 gal water for flushing).
1 PH meter will do the job. You want to test runoff, not the soil itself. Are you using test strips or actual PH meter? You also need a TDS (total dissolved solids) meter to ensure you are properly feeding the plants.
I am growing WW as well but mine is outdoor grown. The temps have dropped down into the 50’s some nights resulting in my stems and sugar leaves starting to turn purple. If you are in flower, purple stems and leaves can be an indicator of Phosphorus deficiency.
Mine is caused by colder temps.
I had a similar situation with some OG Kush stalks starting to get purplish streaks in them. The Ph was low. Three to four days after raising the Ph to 6.5, the streaks faded away.
I am very maticulous when it comes to my Ph. I keep it between 6.5 and 6.8. But I keep my room on the cooler side. Tends to bring out more colors. This particular plant of mine is as healthy as can be, but has maintained some purple since pop.
Soil testers are really not that accurate. If you can get a water tester. Use it before you water and check your runoff after you water.
My gold leaf hydros are in a cold. 58F tent. They have purple leaf stems but are very happy. Could be the cold temps.
