Well, that is why I chose to grow with the Scottyballs method. I have no idea what the PH is. The plant looks green and is starting to pre-flower there should be no Def. as the buffers will maintain the PH.
That being said, changed water last night now @ 900 ppm. The Res. only lasts about 5 days between changes (drinks 1/2 gal. per day) so there would probably be little or no change in PH. The PPM of the waste water was @ 300 PPM from 750 PPM start but, that is with about a 1/2 gal. missing before the change so it could be about 150-200PPM.
Sunny I did see that you were having some issue with your PH at lower PPM so I would think that when you change out and go higher with your PPM that will go away. Don't forget that drift in PH is good for your plant as it exposes the plant to different nuts.
I'll try to get some pictures tonight of My girl
On another note The Train Wreck is really nice smoke My sampling has become a Christmas obsession