Well. . they are at that teenager stage where their hormones are kicking in. They are in part trying to assert their dominance over you.. And in part just being moody teenagers.. And being sexually frustrated.
You need to think about re homeing one of your drakes soon. .or add several more females. The common recommendation is 3 girls to 1 drake. . but it all is dependant on your individual situation and the temperament of your drake. Sometimes if your lucky ducks can be kept in pairs. . but it's not the norm. Having 2 drakes and 1 girl will result in your girl being over mated. . and it's more than likely your drakes are going to fight too.