they look really healthy the leaves you said were yellowing are probably just shade leaves not getting enough sun. when i'm evaluating a health problem with my plants I like to look at 1) the general overall health of the plant and 2) where the problem has arisen and 3)the new growth

I would just try and keep it simple from here on out and continue doing as you have been.

very very nice garden tho for your first time. the background scenery looks like my backyard. i'm sure we are in the same vicinity. I just wish I had privacy so I could grow out in the sun!!