Sounds like a sneeze or cough. Have you looked inside the beak and throat with a flash light for any mucus or yellow gunk? Sneezing can occur if they get something in the nostrils or throat that irritates them. The way she is opening her beak looks like she may have some mucus coming from her sinuses. I would watch for any watery/bubbly eyes, nasal drainage, or swelling around either eye. Corid should not have caused this unless you tried to force her to drink.