I would not wait, I would take him back to the vet asap and I would also ask them to run a test on the droppings to see if there is anything there that should not be. Under the microscope you can see what you cannot see with the naked eye and if they do a gram stain that will show the amount of gram negative and gram positive bacteria. It's normal to have a small amount of gram positive but the gram negative is what you don't want and if there is a good % of that it needs to be treated with an antibiotic. Are you seeing an avian vet?

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