I'm not talking about PH. But PH is probably most important.
Why do you think your water PH test is inaccurate?
I think 7.5 is kinda high for PH and your plants are in a tail spin because of over fertilization. If you live in the U.S. you can send soil samples to your state department of agriculture for testing. But results from the state could take weeks to get back to you.
"An overabundance of nutrients can result in nutrient burn or toxicity and can also lock out other ingredients. Unless the damage is slight, individual leaves do not recover from nutrient deficiencies. Some nutrients are mobile and are translocated from older to new growth, so the damage is seen in older leaves, not in new growth. Other nutrients are not mobile. Their deficiencies are apparent in new growth."
Invest in a Good Set of pH and EC/TDS Meters
"Invest in two relatively inexpensive meters: a pH meter and a TDS meter. The pH meter tells whether the soil chemistry is right for good uptake, and the TDS meter quickly tells growers whether there are too little, just enough or too many nutrients in the root zone. Total dissolved solids (TDS) are measured in parts per million (ppm)."
Feeding pot plants properly is essential for growing clean and flavorful cannabis. In this excerpt from Marijuana Garden Saver, the "Ganja Guru" showcases deficiencies and how to treat them.
hightimes.com