Have you treated them for worms?
Have you treated them for cocidius?
What percentage of protein do they get in their feed? (Ducks need more protein than chickens. I supplement my duckies with high protein treats, chicken eggs, meats, soaked grains, and veggies.)
Any idea how much niacin they receive a day? (Ducks need a lot more niacin than a chicken does. My duckies get it through the veggies and extra protein foods, like eggs.)
From what I understand, from my vet and from reading on this site, ducks usually die very quickly. With an adult human, you will hear moaning, groaning, and a lot of complaining when they don't feel good. With human children, there's very little warning - they crash hard and fast. (EMT training.) Ducks crash hard and fast. (BYC & vet training.)
What I do for my duckies ---
* fermented feed (they love it) which has a higher absorbable protein/nutrient yield than regular feed alone
* supplement the feed with high protein foods, like scrambled eggs, fish, meats, etcl
* allow my duckies to forage all day
* allow my duckies to eat from the garden - it's their buffet (and yes, they do go for things like tomatoes, peppers, greens, some herbs)
* treat my duckies for cocidius every 6 months or so
* treat my duckies for worms every 6 months or so
* offer them natural dewormers (like squash, seeds, etc)
* clean water in their room at night (no food)
* clean water outside in a deep dish secured by bricks (they like to step on the container and tip it over, so the bricks prevent that)
* change the pool water at least once a week (they drink from there too)
* clean their room almost daily (I strive for daily, but life happens)
The duckies free range all day with the chickens. They currently share a room with baby chickens and baby turkeys. The windows are always open or cracked for fresh air at night.
*I say this with hope shining brightly in my eyes* This weekend, they will move to their new winterized quarters and not have to share space with anyone.
There will be sand on the floor. So easy to clean up! And so fast!!!
It would help if we could see the duck set up (housing, run. etc) and know what they are being fed, how often they are being fed, etc.