Oh yes that is way too much drakes. Depending on your weather they can get sexually active early. We have really soft winters the last years; so most are going at it the whole year. It used to be; ducks born early in the year (spring) may or may not lay eggs/being sexually active untill the next spring; but had a good chance to do it the same year. Ducks born later in the year (summer/fall) probably not the same year. Due to soft warm weather they are ALL at it between 4-6 months. No egg-pauses or shedding anymore.. the weather is too off/nice to slow them down.
Did you manage to reduce the drakes?