Nutrient lockout TRAP

not how acid base reactions work. you don't need to use citric acid. if you feel that is a cause use something else. I'd wager that the issue continues. could also be related to your ratio of nutes used in fertilizer. if certain ones aren't at critical levels around roots, the active transport occurring will deplete it and uncontrollable or difficult pH issues can result. h30+ + oh- = 2h2o - the simplest "AB reaction" in an aqueous solution. The result is 2 pH neutral water molecules and not ever "more" free hydroxide (proton acceptor = base) ph is the log scale of h30+ to oh- ratio. if you have way too much garden lime, that's more likely to cause what you see. Every promix bale i've used has dolomitic lime in it and have no problems with pH drift or major shifts. simply doesn't happen in 6 years so far. if you self-amended above and beyond, reconsider that step.