What if the vaginal discharge has a bad smell but with no other symptoms or irregularities, no color/same amount/no itching or burning sensation?

Vaginosis? See MD: Bacterial vaginosis is common, not a sexually transmitted disease, per se. Easily diagnosed and treated. Unlikely other possibilities, but should get examined.

Vaginal discharge: The presence of foul smell may be an indication that it may be an infection, like Bacterial vaginosis which needs to be ruled out sooner than later, and is easy to diagnose and treat. Yeast infection are not colorles. While certain emotional/hormonal/cycle changes may account for certain vaginal discharge, as they say, first things first!