Advice needed, oth ducks have wet feather at the same time and we can't find a reason!

[Snostorm]

Since you have ruled out mites, lice, parasites and they have access to water. I would guess either aging or a diet that is a little low on protein. Methionine in particular plays a very critical role in feather development. I actually started before every molting season mixing in a higher protein feed after I had a duck have issues with wet feather despite access to water and a clean bill of health otherwise. Since doing the protein rotation she molted in beautiful glossy feathers and has not had an issue since.

Sounds like it might be something to do with protein as they are a year old so wouldn't be due to ageing. I'll get some higher protein feed for them, thanks for the help!!