If they are just beginning to lay that can be the reason for laying a smallish egg but rarely do my Muscovy lay a large egg at least not like my Buffs who do lay large eggs. Make sure to have oyster shell out close to feed bowl not in it. They will use it as needed. It’s up to you if you want to go with a layer that is all I can get in non GMO so I mix non GMO scratch grains with it since I have drakes and roosters. If I could find a non GMO all flock I’d def change. Grit they really don’t need unless they can’t find any outside I leave it out year round. Only in winter when there is snow and ice do I see them using it. Once you have them with your drake you can offer a kiddy pool they will most likely follow what he does. He’ll teach them the ropes. My Muscovy drake can just about empty a small kiddy pool when he gets a bath. Lol