I'll give you a bit of free advise:
1. Unlearn everything someone told you in a cannabis forum,
2. MG soil is excellent, see #1,
3. What's with the pH meter and RO? See #1,
4. If you can grow a tomato well, then you can grow cannabis. Give it the same treatment and that includes avoiding "cannabis specific" products. I have come to the conclusion that they do more harm than good. A lot of that blame rests squarely on the shoulders of noobs,
5. If you're determined to forgo a good book on indoor plant culture and a good general gardening forum, thinking your best info can be found here, then buy Mel Frank's 'MJ Insiders Growers Guide'. It will be your shortcut to success,
6. The light biz is another racket. Some of my best indoor gardens have been via using HPS exclusively from start to finish. There is plenty of the blue spectrum in HPS lighting to provide excellent growth. Come to think of it, my avatar plant was grown with pure HPS and the main cola was at least 5" across and rock hard solid.
Good luck,
Uncle Ben