I'm really sorry to hear about your goose. I understand being extra careful after an unexpected loss like that.
You mentioned something about spreading food out? Do you mean on the ground? If so, to avoid food getting moldy it is best to feed from bowls and pick up any food that they spill...
How old is the duck you are concerned about? Could she be a boy duck? Their quacks are different and much quieter than the typical QUACK QUACK QUACK sound.
Also, in case you don't know, when ducks eat their food goes into their crop before it goes into their stomach and it can look very swollen...