Rather than Vinegar, you can use Acetic Acid which is refined Vinegar. Acetic Acid has the benefit of being organic, rather than in-organic like Hydrochloric Acid. This means that it will not to the conductivity of your nute mix.
Someone's done a pretty good sales job on you with regard to the term 'organic.'
First of all, 'organic' doesn't mean 'good', 'better' or 'safe'. It means 'sourced from organic matter or processes.' All organic molecules are made from inorganic molecules.
Second, there's nothing in acetic acid which becomes a nutrient when it breaks down.
Third,
nobody uses hydrochloric acid for pH control!
Fourth, the tiny amounts of pHDown used to shift the pH of a tank is of little to no influence on the EC of the soln. 15ml of pHDown shifts my 125L tanks from 6.2 to 5.8 without moving the EC of the soln at all.
pHDown as you find it in hydro shops is either a phosphoric acid or nitric acid solution. The phosphoric acid version is preferred for flowering plants because the plants will love the phosphorus. Vegging plants will love the nitrogen in nitric acid, but the P based sort will do for any purpose.
pHDown is usually the very cheapest sauce in the shop. There's no economic motivation to use improper substitutes. Save the acetic acid for your photo darkroom.