Any advice, Best food for 12 - 13 week old ducks / chickens. Not kept in same pen??? Nutrena All Flock is not anywhere near me, for some reason (ugh!) I heard about this food. https://www.chewy.com/scratch-peck-feeds-naturally-free/dp/159796 ??? But I am not sure.
IMO, these guys are the experts on waterfowl nutrition, so find something in these guidelines. https://www.metzerfarms.com/NutritionalRequirements.cfm
That is a layer feed, it has too much calcium for birds not laying eggs. Instead of Nutrena, look for Purina Flock Raiser, that will be fine for all of your birds. If any are laying, provide free choice oyster shell in a separate dish.
Good catch. I didn't hit the link. So as she noted, your birds aren't laying so shouldn't be eating layer feed. It would probably be a great food if you can get it fresh and your birds are building egg shells. For ducks, you want to find a feed in the crude protein, calcium and niacin ranges for the age of your birds in the Metzer link I provided.
Mine (Muscovy) get a mixture of plain (broken) chicken feed with water bird pellets from the age of 6 to 8 weeks old. The water bird pellets contain all the minerals ducks need in their diet (except for grit), and the chicken feed gives it that little extra. That one contains split pees, broken corn, all sorts of grains, sun flower seeds and a bit of small grit (which ducks do need too). They are getting this mix all year round. And sometimes they get a little special treat, in the form of live mealworms (they go CRAZY over those) and once a week a small handful of live wax worms (right before winter season). Funny to see them eat those by the way. They first carefully crush them (SPLAT) to then swallow them. The mealworms on the other hand are just gobbled down in no time.