I agree with everyone above about smaller pots, 3 gallon is a good size. Make sure you have drainage.
I plant all my germinated seeds in
Fox Farm Happy Frog soil, it will not harm your plants. Don't add any supplement nutrients during seedling stage.
Yeah, I just recently started my current grow in
Happy Frog with a touch of dolomite lime to help hold a 6.5 pH. Only supplement I added was, after seedling stage, Epsom salt in tap water when the pots were dry-ish. Then when I potted up, I went from 3-qt pots to 3-gal fabric bags containing Ocean Forest and lime. I’ll do it this way again.
I do recommend that the OP::
1) calibrate the pH meter before the grow, and
2) get an idea of your soil’s initial pH, either a slurry test or measurement of the runoff pH after the 1st watering.
Most of the issues I’ve had as a newer grower have seemed to have a significant soil pH component at their, uh, root. . Dolomite lime seems to keep me in the sweet spot. Now I just need to remember to calibrate before the grow…
Edit to the OP:
Depending on the size of your autos, you may be ok with those tall pots, but watch in case they get top heavy.