So very sorry! great news on the one you were worried about. They actually need to be on some form of niacin till at least 10 weeks of age. You can substitute Nutritional yeast along with the liquid b complex or just stick to the liquid B complex but even after my ducklings are past the 10 week...
Hopefully the little one is doing much better now. Drinking and eating a little are good signs. Other than support that’s about all you can do, other than vet care. hopefully the liquid BComplex will be enough.
It doesn’t sound like anything else could be the cause they have been where they couldn’t get into anything toxic. Unless you take them to the vet and get necropsy done on the ones that have died you have to try with what you have. Get the liquid b complex started and hope that is what it is...
Give it straight just a drop at a time. If it's not almost gone, you don't want to cause it to aspirate. If she can't hold her head up it might be too risky but you make that decision since your there. If you think you can get her to swallow.
Any heat source? Are you using cold water or Luke warm for drinking? Supplements should be Liquid B complex also from TSC you’ll find it in the cattle dept? It will say injectable but peel off the foil and use a dropper to get out a ml and put over the meal worms so they get full dose. If it is...
Welcome to BYC and sorry it is under these circumstances that you joined. Where are they being brooded? What type of bedding? Feed ? And are you using any supplements? Very sorry for your loss. Also where did you get your ducklings?