Brown spots and lower leaf yellowing.

Hey guys! So after quite a few issues on my first grow, I finally got most of my issues in check. I found I was using very hard water (7.5 pH and 740 ppm tap water). I also had heat issues, where temps would get up to 81-85. Again, I have all that in check now. My lights should also be OK, with PAR of around 200-230. I am feeding them now with GH at 1/3rd strength.

So I have been dealing with yellowing leaves my whole grow. I chop em after they turn very yellow. Recently, I am also getting brown spots, and am wondering if anyone could help me identify the issue on these 2 plants since I am such a newbie when it comes to growing. Ignore the white dust on the leaves. It's not mold. It's clay that got sucked in the central AC when my vacuum shit out on me lol!

in pots that size and depending on soil type, you shouldent need to feed forvquite some weeks yet
whatsoil is it?

the soil is Black Gold. It has a little fertilizer in it, not much though. I started to feed them since their leaves started turning yellow, they showed all the signs of deficiencies. They were in seedling mix before that, which had no nutrients in it.

i think you have that wrong, i just googled it and it says its hot and should be left for several weeks. another says its top soil. so im confused

How do you use black gold fertilizer?
Established Plants: 2 cups for every inch in trunk diameter (measured at 4-6 inches above the soil line). Mix thoroughly in the soil just inside the drip line of the plant. Fertilize at time of planting and every 6-8 weeks throughout the growing season

I'm using their soil, haven't tried their fertilizer. Their potting soil has 0.09, 0.03, 0.03 for the included fertilizer. Any ideas on what could be wrong?

Any ideas on why the lower leaves on my plants keep yellowing, and random brown spots on leaves? I sprayed with neem oil about a week ago, so I don't think it is bugs. Not seeing any.

I have brown spots on one of my green leaves too now apparently. (Again, ignore the white powder. It's clay, not mold).