I did not see if anyone answered the layer pellet question. So, sorry if this is duplicated. I would not feed the drakes layer pellets. Just get a good quality all purpose pellet and supplement with oyster shells for calcium for the hens. The drakes will not be interested in it and the hens will eat it as they need it. The layer pellets have too much calcium for drakes and it can present a problem for them.
Also, hope you can work things out with your flock. Keep a close eye on the boys, as they mature the competition for the females will increase and the overmating can really hurt your girls. Plus, they may start fighting. Not always, but it is a possibility and it will become dangerous for one or both. Is there anyway you get a few more girls and make two flocks that you can keep separated? A lot more work, I realize, but for safety's sake, giving each boy two girls and keeping them apart might be safest for all involved.
Good luck, they are gorgeous ducks!