Op mentioned, ph probe not working .
Your source water is suspect.
However, I see yellow leaf very quickly when I dry out a plant.
Did these things get really dry, a few days ago ?
Your liquid rock water is very hard for plants to stomach to begin with, my tap is the same.
Dry soil , nutrients , and high Ph creates a micro apocalypse around the root zone.
(
Yun-Im Kang, Jin-Myeon Park, Seung-Heui Kim, Nam-Jun Kang, Kyoung-Sub Park, Si-Young Lee & Byoung Ryong Jeong (2011) EFFECTS OF ROOT ZONE PH AND NUTRIENT CONCENTRATION ON THE GROWTH AND NUTRIENT UPTAKE OF TOMATO SEEDLINGS,Journal of Plant Nutrition, 34:5, 640-652, DOI:
10.1080/01904167.2011.540621)
“
The responses to the pH levels differed by the nutrient-concentration levels. The unsuitable root zone pH, pH 4 and pH 8, caused more reductions of transpiration rates, stomatal conductance, and evapotranspiration than pH 6 does under high nutrient concentrations, specifically pH 8 strongly depressed these. At pH 8, fresh and dry weight and areas of shoot and root sharply reduced more than at pH 4. Total nitrogen (N) content in shoot and root was not significantly affected by pHs and nutrient concentrations. High pH and high nutrient concentration level increased magnesium uptake, but decreased calcium uptake.
“
So, in my experience losing bottom leaf = too dry.
Blacking off bottom leaf = to wet.
Rusty lower margins = Calcium trouble
Can’t say a solution; I have the same water (180-260 ppm , TDS) and the same problems.