I agree with Daisy's first post: water, water, water and flush. Maybe take a pH test, then MAYBE, if needed, AFTER trying the flush method thoroughly, a little diluted vinegar.
The ideas about diluting it a lot, distributing it uniformly, and keeping stronger vinegar off the foliage also sound right to me.
I agree that sodium hypochlorite ("regular" bleach) is a strong base in the oxidation-reduction sense, but I didn't realize it was also an acid-base base.
If the soil pH is still basic after thorough flushing, for example if the flushing water is also basic, some soil acidification wouldn't hurt. If the issue is no longer urgent after flushing, you could also do some long-term acidification with agricultural sulfur. Soil microbes turn that elemental sulfur very slowly into dilute sulfuric acid, which instantly combines with basic soil to release sulfate ions, which plants can use as a micro-nutrient.
I wonder what hydroponic people use to raise pH instantly? Very dilute nitric or sulfuric acid?
I used to basify solutions (I'm pretty sure that "base-ify" is not a word!) using a very little hydrated lime greatly diluted in water. That can be as potent a base as sulfuric acid is an acid, but using only very little, and letting it sit sealed with water for a few weeks before using, moderates it's strength.
