Was ask about this.
I am running my base at 300 to 350 in veg and 400 to 500 in flower. Have my rez at at 1.2 EC and over a 24 hr period my pH floats from a starting point of 5.75+ to 6.0. I finely figured out to let my nute mix rest for 24 to 48 hours prior to putting it in the rez and not to constantly recirculate my lower and upper rez's and it helps keep my pH stable. The ladies are looking great no overfeeding here, Less is More!
Here is the last mix I made on Monday morning and put in the rez Tuesday night. This was 6 gallon RO and 9 gallons rainwater.
What I have done this grow is at the end of a week's rez use, which I fill ever two days, I let the rez get down to around 6 gallons, pH to 5.8 and run my drip till I empty the rez, this flushes my ladies. When done my EC of the waste water was 1.3 to 1.4, taken at different points of flush, and pH is right at 5.8. Then refill the lower rez with the new nute solution and pH in that rez before I pump to the upper rez for distribution. This has really worked well and I will continue doing this throughout the grow. When I do this type of flush I also add the high rate of SM90 15 ml/5 gal for fungal gnats. Had them fuckers destroyed a grow. I do this instead of adding SM90 to my rez for daily distribution as I have found that SM90 causes a oil slime in my rez, Seems to be working fine this way.
I am supercropping, LST, binding and tying them ladies like I was a masochist, LOL
I know I will love the results but it is requiring a shit load of work. And I this is supposed to be a HOBBY.
GR