By the way my plants look like shit, and my res keeps wanting to come back up to 6.3 PH. I'm struggling, and it's pissing me off.
I've done a lot of research into ph the last couple of weeks and these are my conclusions (don't take it as gospel, though; do your own research
).
First off, the ph rise you speak of is PROBABLY normal. It means your plants are growing and your roots are active and taking up nutrients, particularly nitrogen. Nitrogen, in its base form, is acidic; the more that is used by the plant the less acidic the solution becomes (ph rises).
Most everybody who has grown DWC has experienced the rapid growth that takes place starting around week three of vegging...the plant is taking in nitrogen rapidly during this stage and you will probably experience an associated rise in ph. This is normal so long as the ph stays below 6.5 (I would even say 6.8 ) and you probably don't need to worry about it. Using ph down is probably fruitless and may even be detrimental (rapid ph swings can cause root shock).
IN MY OPINION, and what works for me, is if you want to lower ph, especially during veg, then ADD MORE NUTES, particularily nitrogen (or the Grow nute). I add 1/4 strength Grow to my top-off water to help replace the depleted nitrogen (while keeping an eye on the overall ppm).
And if you journal your ph levels, you may notice that the ph stabilizes or even drops late in the veg cycle; the plant is telling you that it is ready for flowering and is no longer using as much nitrogen. This is technically when you should change to bloom nutes.
People who switch to flower nutes too early (or at the same time they flip to 12/12) when the plant is still growing will often see the lower leaves yellow. This happens because the plant pulls nitrogen from the older leaves if the roots can no longer find a sufficient supply. I usually continue my grow nute regimen 1-2 weeks after flipping.
So you can go by ph monitoring, or alternating nodes, or reading Tarot cards to determine when the plant is ready to flower. Whatever works.
You say your plants look like shit: discolored leaves? Stunted growth? Drooping? Any updated pictures?