Never ever shoot liquid down into the bill It's just way to easy to get it into their lungs.
With young ducklings I much prefer giving it to them over a special treat like mealworms or peas smashed up, I also put it into the drinking water.
@Angelove you are doing great. Giving it to them slowly...
I don't know about injection but @casportpony or @Isaac 0 could probably help you there.
If you follow the info on the link I gave you. I usually get my dh to hold the birds and that gives me 2 hands to work with one to open the bill the other to put the liquid down the right hole. you need a...
At the age they are unless your offering chick grit what you can feed them to get the liquid b into her is limited. Some ducklings don't mind the taste and will gobble the peas right up. But unless your offering chick grit I wouldn't even give them peas. They have no way to process anything...
The B complexes in the article are the safe ones. Once you begin seeing the leg issues the B complex is the best way to help and yes orally 1 ml per ducklings over a tasty treat or small amount of feed just to make sure they are getting full dose.
Let us know how this little one is doing. It's...
TSC carries it. Ask for it. Because there is no telling where they may have it in the store.
I don't have a TSC close so I had to order online. Some other feed stores may carry it too.
https://www.backyardchickens.com/threads/niacin-deficiency-in-waterfowl.1367557/
Bless they definitely need to get started on some vitamin B complex ASAP. It works wonders and once your seeing a problem is the best to use to get them over it.
:welcome