https://www.backyardchickens.com/th...nd-supportive-care-updated-5-14-2018.1048620/ go here and scroll till you come where its shows how to give meds it will show you exactly how to give it By mouth. Wrap the duckling in a small towel before so she'll not be too stressed out. I would def be giving to all your ducklings I used a quart of luke warm water to a dropper of Liquid Bcomplex for my ducklings. Any that wouldn't take it over something and had an issue that needed it gets it orally.