Lower leaves turning yellow and getting crispy

Looking at the image you posted. It seems you have issues with a few leaves. Could be from the neem oil you use on the plant. It's always good to know the ph of whats going into the medium and out. This can help you narrow down issues with a plants health.

This is, honestly, completely natural and nothing to worry about! Trim them off... they're not doing anything anyway... the leaves you want to be concerned about are the 5-fingered leaves - not the single or even the 3-fingered ones! Calm down... don't stress... I screwed up my first ever grow to a fare-thee-well and still got a decent harvest out of her... I've screwed things up in lots of subsequent grows, too, but learned a lot along the way... and weed is pretty tolerant for the most part... no need to stress out over something that isn't a problem! Good luck!