My friend's Muscovy ducks have been losing all of their feathers including their down and are soaked
It sounds like they are going through a moult and need to be kept inside when it is rainy and cold like that. They will not be water-resistant again until all their feathers come back in, and they will also not be as able to deal with the cold. Is she able to keep them locked inside somewhere for awhile? Maybe a barn during the day so they have some more space to move around, then into a secure duck house at night? I don't know what her usual set up is for her ducks, but they need to be kept inside and protected from the weather right now or they may not make it.