they look like hens to me but keep a lookout for a curly tail feather its a sure sign of a male.Also the females quack loudly and the males have a raspy voice.Sounds like a whisper.
They are very pretty though.Grats
Boys don't get their boy colors for several months, same with the tail curl. You should certainly be able to tell by the voice at this point. If they have similar voices, they are of the same sex and that's why you feel unsure. If you have one of each, the voices will be so unbelievably different, you'd know already. As someone already said, the girls have a very raucous loud kind of honking quack. The boys are much more whispery. I often think it sounds more like the boys say buk buk than quack. Here's a good site for hearing the voices of male and female ducks. http://www.majesticwaterfowl.org/artquacks.htm
Gosh , right now they look like hens, but I'm wondering. Cause they have different colored bills. And the darkerone with the lighter bill, has what looks the a seperation on the neck. possibly getting his white ring?
I have 6 mallards right now at 9 weeks looks just like yours but smaller..I aknow I have 3 males and 3 females..3 quack and 3 dont...LOL , I also go by beck color my boys have always been lighter the girls becks are darker but not always is that the case....See any green shimmer on the head?
I think Quackers could be a male. I am going by bill color which tends to be greener. Females tend to have a yellow/brown blotchy bill.
But you won't know for sure until they start quacking.
At nine weeks, they should be quacking.
Females will be loud Ka-WACK-kwak-kwak.
and males will have a softer 2 syllable
wahk-wahk wahk-wahk vocalization.