Updating from desktop because I am old and my beat-up hands don't play nicely with touchscreens.

Ok so, in an attempt to 1.) eliminate the extra phosphorous potentially added to my system through the use of phosphoric acid (the stuff many pH down products are) I changed things up this grow and started with citric acid. Normally in DWC I'd see drift from 5.8 to 6 over the first few days and then a steady drop until res change.

Using citric acid I initially pH'd to 5.4ish allowing for my basic well water still in the system and not in the res to cycle through. 3 hours or so later I was up in the 6+ range. Before going to bed last night I pH'd down with citric acid to 5.4 again. At this point my runoff was reading 6.4.This morning...the res is back up to 7. I go down a rabbit hole of science and highschool chem and I chicken little my butt in front of all the guru growers I know and the consensus is the citric acid is the issue. Why though?

Here's what I vaguely understand about the science (please correct me and educate me if I'm off on my thinking):

Citric acid is a weak acid. Not weak like won't ruin your day at pH 1.5, but weak as in lacks a massive difference in charges in associated ions. I take this to mean it breaks down really quickly in water. Citric acid also forms chelates, which means it bonds to stuff like calcium and iron to make them more water soluble. This is great if I were using it to make my own dry nutes....not so good for pH down :D

Good lord this was an unpleasant experience. I'll dig in deeper next time before frivolously ad-libbing during a grow.

ANYHOO....

All three ladies are looking fine. I'll keep monitoring pH but I've gone with phosphoric acid now. My EC has rose to 1.0. I don't feel like increasing nutes or even trying to replenish what I may have burned through while adjusting pH. The little ladies should be good for a couple days with a weak nutrient solution. At this stage the cotyledon should still be feeding them.