Vinegar doesn't act as a buffer, it acts as an acid. So if you had used to much your pH probably just got to low. I use Braggs organic unfiltered apple cider vinegar if I need to tweek my pH. Plus the unfiltered vinegar has some goodies left in it like Potassium.

I use it as minimally as possible though, because from a past experience if I used too much my soil mix would go very acidic in a hurry.

When you say an "organic" pH up or down, what do you guys mean?

Isn't the difference between "organic" and "chemical" that in water, the organic nutes don't form an ionic solution? So how can anything that alters the pH be organic (or not show up on an EC/tds meter?)

I think the idea behind it is an organic product with an acidic pH. Say organic lemon juice, organic apple cider vinegar, Products like that.