First Grow In Years... Zinc Problems?

Hello all! I havnt grown a crop in atleast 5 years so I'm a little rusty, I have two strains, cherry pie ( GDP and Durban poison) and angel cookies(GDP x GSC) x GSC). I'm growing in a 5x4 closet with two 400w hps lamps being cooled by a vortex fan pulling air through both cool tubes. I'm doing scrog Temps are 80 pretty consistently, humidity around 30 to 50 percent. I feel with 2 tsp bc boost to 1 tsp of bc grow, cal mag at half strength. At first I had bad ph problems which I figured was due to me poorly adjusting ph before adding nutes, which further buffered and lowered my ph. I do not have a ppm/ec meter.
The plant's new to new/mid growth have been showing signs of slow growth, small leaf syndrome, twisting tips, yellowing between veins . Old fan leaves are still green ( showing slight signs of old zinc deficiency but very healthy) I believe it to be a zinc issue, at first I though it was deficiency but I started to think toxicity! For a while my ph was high, mid 7s and I had to buy a new ph meter. Then I started doing it wrong and while I was adding water that was ph 5.8/6. Once everything settled my ph would read as low as 3!!!! So I flushed the roots and res and wtf still my ph was still reading below 5 in the res! Fast forward two days of flushing and running clean water through, also fast forward to a dropped in res ph meter.... I have no meter until tomorrow and have no clue what is really wrong. Here's a pic.