Know a natural remedy for a bacterial infection for a bird?

My bird is having watery droppings for over a week. I think she may have a bacterial infection. I started putting vitamins in her water before her dropping changed. I recently read that vitamins in the water can cause bacterial infections which will cause watery droppings. The vet will cost a lot & I’m scard of what they may give her. Is there a natural remedy I can use instead?