Hey man, I don't run hempy buckets but I'll try to answer your question honestly : the pH of rain water is 5.5 , in nature the soil will buffer the rain water to 6.5, differebt nutrients are absorbed at different pH from 5.5 for micronutrients to 6.5 for other nutrients . At 6.2 you pH is simply too high for a hydroponic grow - you want to be at 5.5 to 6.0 max so your plants can absorb all the nutrients it needs. Right now you're seeing phosphate deficiency due to high pH. Get that pH down and the problem will stop spreading. Hope this helps ! 🚀