It sounds like behavior related to vitamin deficiency. That would be unusual for 3 day old ducklings. How old are the ducklings? What is your brooder set up - heat and cool ect. What are you feeding them?
I would probably try feeding them some eggs. With ducklings niacin deficiency is common. Some use B complex liquid I think it might be an injectable for cattle that is feed to ducklings orally. For wry neck vitamin E. I know there are supplements such as rooster booster, but I have not used them and do not know which vitamins they contain.