Well if using vinegar and baking soda are actually the only change that's happened recently I'd say that's probably your problem. More specifically, it's probably the baking soda.

Baking soda is sodium bicarbonate. Sodium is bad. That's why it's not used to make commercial plant products.

Have you ever heard the phrase "salting the earth"? It goes back to around 1300 BC when the practice started. To punish people sometimes their land would be salted, which caused all the plants to die and rendered the land incapable of supporting crops for years. It wasn't done commonly because of the enormous value of salt (it was often used as currency and people being paid in salt was the source of another common phrase of a man being "worth his salt".)

But in short, if sodium levels build up around a plant's roots, it dies.