Here's a short vid of the ducklings eating mashed peas with applesauce and a tiny bit of brewer's yeast. They go nuts for it and half a cup is gone in about 2 mins. They are starting to become a handful in their current brooder box and will be moved soon into anther one. If you've ever raised chicks but not ducks, know now that ducks are like 5x messier with everything. I'm now changing bedding every 6 hours or so. They are big enough that I need to ditch the water jars and move onto deeper water bowls and a different bedding system.
Here's an okay primer on the subject,
https://www.fresheggsdaily.com/2012/02/basic-duckling-care-raising-healthy.html 