You might read the article below to get the best explanation.
Baking Soda and Vinegar for Hydroponic Nutrient pH Control
by Michael E. Basham
Answer: Michael- It is true that baking soda can raise pH, but I do not recommend using it. Chemically, baking soda is Sodium Bicarbonate. High levels of sodium are like trying to grow plants in salted soil. In addition to that, the presence of Sodium compounds will prevent the plants from taking up Calcium.....which will cause all kinds of problems with nutrient deficiencies (Nitrogen is a mobile nutrient, but is only mobile to the plant in the presence of Calcium. Other nutrients will only be taken up by the plants along side Calcium).
You're really testing me on my chemistry today, lol....
Vinegar's chemical composition is CH3COOH....it is just a bunch of Carbon and Hydrogen and Oxygen. On it's face, none of these would interfere with nutrient uptake. However, vinegar is only a weak acid, which means you may need quite a bit of it in order to keep your pH level correct. Once you begin using more substantial quantities of vinegar in your nutrient reservoir, it may not be so cost effective anymore.
Also, even though the Carbon and Hydrogen may not affect nutrient uptake, they still add to the total TDS (or EC) of the nutrient solution....which means the more you use, the fewer nutrients you can legitimately have suspended in your nutrient solution without burning your plants. This is why commercially available pH down is made of Phosphate compounds....they not only bring the pH down, but are also available to the plants as usable nutrients. This is not the case with vinegar.
In reality, I don't know for sure what would happen if you used vinegar to control your hydroponic nutrient solution pH. However, I have enough concerns about it that I would not try it myself (at least not on a big scale, or on an important plant or crop). If you do decide to try it experimentally, be sure to let me know how it turns out for you....I am curious to know for sure.
The best way to avoid the expense of pH down (and to a lesser degree, pH up) is to choose your hydroponic nutrients well. B.C. Nutrients mix up at the right pH, and the pH changes very little over time. The same is true with Canna Bio. Other nutrients require a LOT of pH adjustment, like Earth Juice. Hope this helps Michael, and Happy Growing!