Regarding that you somehow "ended up having something toxic" in your feed water, it looks more like nutrient excess (and/or nutrient lock-out from excess of other nutrients) or media/soil pH imbalance.
What water are you using; does it have high salts/ppm/EC; what media/soil; what feed and supplements at what dosages have you been using in this bloom phase? If using base nutes that require pH adjustment [seems outdated/legacy to me; there are good options for nutes that with good water don't need this, such as AN pH Perfect and MegaCrop], what do you adjust to and, perhaps the source of your problems, do you properly store and periodically calibrate your pH meter?