What kind of PPM meter are you using? Do you know the conversion rate to EC? I keep mine around 2.0-2.2. I personally leveled out @ 1100, with no rise @ all. They are consuming 200ish and 3 gallons a day. My advice...Flush more often, and back off till your PPM stabilizes. Other than that your plants look amazing, can't wait to try scrog.
She's drinking so much that it's basically a fully refreshed reservoir every other day. That said, it probably wouldn't be a bad idea to run a couple gallons of filtered water, without nutes, through the system before draining and refilling with some 1.8 (900 ppm) solution. I know that I'm being a little aggressive by going for that 2.2 (1100 ppm,) and I've heard that Pineapple Express can be sensitive to the nutes. Considering that light is most certainly the limiting factor (and not nutes,) I'll dial it back to 1.8 (900 ppm) after a rinse through tonight.
EC to PPM, multiply by 1,000, then divide by 2. EC 2.1 x 1,000 = 2,100. 2,100/2 = 1050 (PPM)
Oh and I know it was probably a typo, but that's just one plant in there, ha!