Well, first off: Welcome to the forum!
You’ve put a lot out there to digest. Here are a few high spots that popped out:
Hard to tell how far along plants are with those pictures: white light is best.
This is nowhere near enough light to flower off plants. Here’s the deal: light is the engine that drives all processes within the plant. Without adequate light the plant will suffer with long node spacing and loose, airy, low potency flower. It also makes it harder to supplement when nutrient demand is lower than is expected with these products.
This device should be bent into a horseshoe and deposited in the nearest circular file lol. They are completely worthless. Good digital PH and TDS meters are readily available and one brand gets a lot of use here: Apera.
https://www.amazon.com/Apera-Instruments-AI209-Waterproof-Accuracy/dp/B01ENFOHN8/?tag=greenrel-20
Unfortunately there is a lot of misinformation and hype regarding lights. LED’s are the state of the art and good lights blow away anything other than sunlight. The operative is good: almost anything on Amazon is junk. Other than a couple of lights buried behind all of the ‘China’ lights, it’s a waste of money.
Brands I’d recommend: HLG is top of the list, CHILled Logic, California Lightworks, I think Gavita is making LED’s but start with HLG (Horticulture Lighting Group).
Download the Marijuana Grow Bible ilovegrowingmarijuana.com
Some material is dated but will give you a better idea of growing.
I’ll put up my current journal: read it over if you like and ask me questions: that’s what I’m here for.
If this is something you wish to continue with, it would be good to look at what your budget is for both space and $$: this will be helpful when it comes time to point you down the path as it were.