I've had great results with just a handful of pumpkin seeds a few times a year.
Have you checked your program by having fecal exams done for parasite eggs? Adult birds can harbor parasites without clinical signs or visual evidence of worms in the stool. Pumpkin seeds are not a very effective dewormer. Having stool samples checked can both identify whether you have a parasite problem, and what the best treatment is if you do.