Tryin to figure out what I’m doing wrong

Starting a diary to keep track and figure out what I’m doing wrong. My plants have been doing great until 1-2 weeks into flower where they turn yellow almost overnight. I start seeing burned leaf tips but also deficiency where bottom leaves start turning yellow. Then the whole plant. I was using tap water (ph=9 ppm=300) I always ph to about 6.2. And I’ve added very little nutrients, just a little calmag. Which might be my problem since my tap probably has some. But the runoff in early flower reaches 1400ppm. Which is why I think it might be nutrient lockout? I’m starting this new grow with spring water. My first 2 grows were incredible and then I moved and now I keep having the same issue. It’s frustrating but I want to learn from my mistakes and grow some beautiful buds. Any help is appreciated