No, you don't need Scratch. Scratch works against a nutritionally complete feed. Its useful for training purposes, if that's your desire, or to encourage them to scratch up a particular section of soil (like hardpan/clay), but honestly, you can throw regular feed and likely encourage the same behaviors. Its completely unneeded.
Nutrena has both a non GMO "Natural" (Nature-Wise) line and an Organic line. The Nature wise is relatively easy to find, the Organic, less so. Both are good feeds. Purina ALSO has an Organic line now, though I've not seen it.
A number of posters use the Kalmach Organics, which are mostly whole grain as well. Best results come of feeding it as wet mash, fermented feed, or even sprouted so your birds dont pick out favorites and leave the rest to birds lower in the pecking order, contributing to nutritional imbalance. That's not specific to Kalmbach, its the case with any whole grain feed.
What you are looking for is a high niacin feed, 18-20% protein, calcium about 1-1.5% (offer oyster shell free choice on the side, grit on the side), fat in the 3% - 4.5% range feed. Likely sold as a"All Flock" "Flock Raiser" or similar. MOST feeds don't disclose niacin levels - ducks need far more than chickens, but the "extra" niacin isn't harmful to your chickens. You may have to contact specific manufacturers for their levels. Prior posters have inquired of Purina and Nutrena, both had adequate for ducks levels of niacin in their flock raiser/all flock formulations when the question was put to them.
You should also be aware that its VERY hard to hit desired levels of a limiting amino acid, methionine, in organic feeds. A small amount of synthetic methionine (dl-) can be added and still maintain the "organic" designation. No soy formulations have even greater difficulty reaching targets, and vegan formulations find it near impossible.
In older, developed birds, its less important. 0.3% - 0.35% is considered adequate for both breeds. In juveniles and hatchlings, demending on age, breed, etc, levels up to 0.6% are recommended in the literature. You simply won't find those in organic feeds - and birds raised on lower (0.35%) levels will likely appear healthy, but will never reach their full potential. Its a key component to early muscle development, and needed in connective tissues throughout the bird.
Seeing organic fish meal, or organic porcine blood meal on the ingredients label, is very reassuring. If you get the choicebetween two organic feeds, and the first ingredient in one is wheat, soy, or alfalfa, and the first ingredient in the other is peas - pick the one that isn't peas. The reasons would require a much longer post.
Finally, you may find success with local mills in terms of both price and freshness. I'm in FL, so no personal experience, but
this group is out of Cashton, WI claiming Organic feed. Unfortunately soy-free (I warned you), but using fish and crab meal. I can't get an actual ingredients list to load or a certified nutrition label (BAD internet connection on my cell phone), so I am NOT recommending. Just suggesting you may have options outside of the national brands.
Oh, re: protein. Don't go over 24% for ducks, particularly young ducks, or you significiantly increase your chances they develop angel wing. and there's no benefit to feeding chickens over 20% after 4-5 months, which is just fine for ducks of all ages - even then, the benefit is weight gain and early condition for table, a less important consideration in layers. Which is why I recommend the 18-20% for all your flock, all the time.
