I would suggest using ivermectin orally or topically in the future to get rid of mites and worms in the future.
Ducks only take a load of mites when they are unwell. It's a good warning sign.
I wouldn't take a duck to a vet to be wormed.
In the future, I would look for the many signs of worms, offer squash seeds seasonally that act as a natural wormed and improve their environment. Ivermectin works, panacur is easier to dose.