I agree that they could have more protein, especially since they are outside more and grazing on other things that will lower their overall protein even more. There are several all flock type feeds that are 18% protein. With my ducks it was right around 5-6 weeks that I first heard quacks, so you should be able to sex them soon. They would mostly peep and every now and then one would let out an adult quack. It probably took another week before I could figure out which one it was coming from! Generally if I walked away from one, once out of sight, the one left alone would be the one to make the noise, the one I was holding would remain calm. Keep an eye on them. Set up separate feed/water stations so one can't prevent the other from eating and drinking. Hopefully they settle down.
