Vitamin B in general is very important for proper function of you stomach (for both transportation and gastric acid production)
Antibiotics and Proton Pump Inhibitors and some other drugs disrupt the production of Vitamin B or B-12 (basically all the B-complex) and that is why the imbalance of digestion comes in. It is not necessary Antibiotics killing off the good bacteria and leading to candida overgrowth.
A healthy person should produce 2 liters of gastric acid per day. This is a lot of acid for proper digestion. If you can produce 2 liters of acid per day, I bet you would feel like an OX.