If available use the Purina line....Start N Grow then Flock Raiser then the layer. You can see them here: http://poultry.purinamills.com/NUTRITIONMANAGEMENT/FeedTypes/default.aspx If not available then NON Medicated chick starter mixed 50/50 with turkey wildgame bird starter. Give them fresh green daily...lettuce cut up and floated in water. Frozen peas thawed. It is good for them and they love it...helps you bond with them also.
They will eat scratch but it is not going to do anything nutritionally for them. The wheat does little to nothing as far as nutrition either. They need to be on Flock Raiser when not laying and Layena when they are laying.
Oh wow I have no idea. Call a feed store and ask them specifically what they carry for waterfowl. They need more niacin than chickens and less calcium.
Feeding ducks corn is like you living off sugar only. Not a good diet. You need to find a feed store and food designed for ducks. Katharina