when in the pet clinic, I just saw them spent some time examining the dropping I brought to them, and that's how they found out about the parasites. But I'm not sure if they checked for canker and yeast.Did he do a cropsmear to check for canker and yeast? Hopefully it's the fenbendazole that made him feel bad and he will recover if you stop giving.
Also referred to as TRICHOMONIASISThose are starvation droppings. He is either not eating, or if there are food in the crop then it's not digesting. He is probably not flying because he is weak. If the crop is empty, you can handfeed him defrosted green peas to keep him going until you can figure out what is wrong.
Take a flashlight and check deep inside the back of his throat for any yellow or white growths that can be a symptom of canker. Drinking excessive water, losing feathers on the breast and making rotating movements of the crop after eating are other symptoms.