Two months ago I also had 2 ducklings in with my 6 chicks and had to add nutritional yeast to the chick starter because it did not have the added niacin that the ducks needed. I switched them over at 4 weeks to a non-gmo organic grower pellet that was nutritionally made specifically for ducks and chicks and said could be started as early as 4 weeks (most grower pellets say 8 weeks). I did this because the chick starter was "medicated" to help prevent worms and they say that is bad for ducks... but mine thrived for those 4 weeks, with no problems. The pellets were a bit difficult at 4 weeks but they managed perfectly fine with deep water bowls for the duck's nostrils to take a sip while eating, I just kept the bowls close to each other. The ducks soon started to eat greens like dandelions at 4 weeks old so they also got extra niacin while free-ranging too, and we fed them worms for more protien. No problems with nutritional yeast for the chicks at all because it is water soluble.
