Ok another hard lesson here don’t feel bad most people do this their first time. With your ph meter you also need reference solution to calibrate and check your meter and calibrate it regularly like every 10 days or so or check it if it’s right you don’t have to calibrate it.
Boomerang is a very good comeback solution from fox farm and i have great results with it. I don’t use fox farm soil just their nutrients i like pro mix soil. Also do you have a humidity reader it’s like 9 dollars on Amazon reads relative humidity and temp with a high and low .
I have hard city water so i use a PUR filter that attaches to the kitchen sink its cheap at Wal-Mart and work’s great go to the sink and turn on the water and flip the lever and fill up the jugs. I was kinda like wow when I opened up a filter and saw everything it was catching and my plants seemed to like it and grow better.
The flower blooming trio of fox farm is very nice to open sesame beastie blooms and cha ching and get bembe believe me it’s worth it the dirty dozen on eBay for 84 dollars is well worth it the sledgehammer will help break down the salts when you flush. I feed at half strength of what the feeding schedule says i would do that especially if you used ffof soil. But i don’t get nute burn by doing this. Also Epson salt is a must have to one or 2 tablespoons to a gallon of water on a water day once every 3 or 4 weeks. My journal is 6 strains of fun
I went through some of the problems you are having hope this helps you