Looking at you pictures I don't see anything to worry about. You never said what stage your plants are at but, from your pics, I'm guessing week 6 - 7?
What I'm seeing in your pics looks like leaf senescence. After week 6 some cultivars start to cannabalize the leaves of stored food for the final push so you'll start to see more leaf death the closer you get to harvest.
In other words I would continue doing what you were doing before(other than pre pH) and continue monitoring the situation. I would also suggest you pick up a loupe to check your trichome development. That is the best way to figure out how close you are to harvest. I don't really see a deficiency.
As far as watering, I use the light pot method. If you are familiar with the concept then I won't go into it but if you aren't just ask and I'll explain proper watering techniques.
Can you take a picture of the entire plant to get an idea of what it looks like overall?