We don't mean to sound overbearing, but waiting for the ducklings to be big enough to be in with your girl might be a bit too long to keep her safe. Can you somehow separate two of the boys out and just leave her with one drake? Even if they are not mating right now, I assume you cannot watch every minute and it just take a second for the hormones to kick in and for them to want to mate. Personally, I still think one drake and one hen is not great, but I did it for a bit when I lost one of hens. However, my drake is pretty laid back and he was not constantly after her. But I got a second hen as soon as I could. Now he has 8 girls, so everyone is safe!! If you can put the most mellow one with her and keep her safe till the babies are big enough, that would be good.