Mine are the same age. I can tell by their quack or lack there of. I have 1 female and 2 males. All 3 look the same. But have different sounding "quacks". I can not see a curled tail though. On my Pekins that are 2 weeks younger, the males have the circled tail feather. And also have the quack and no quack.
You cannot sex them by feather at this age. They all grow in the same pattern first and then, later, molt into either male or female plummage. That said, if you got these from a hatchery bill sexing tends to be fairly accurate on hatchery strains. Those with a green tint to the bill are males, those with bright yellow/orange bills are female. The third picture down, for instance, is a male. No doubt in my mind. The top picture also looks to be male. The second picture is blurry and iffy. Possible female. Clear close ups of their heads would make it a lot easier to say.
As srpaint says however, the quack is the most accurate way to tell at this age. If you don't have clear differences in quacks, I'd say you have all males. The females QUACK and loud, the males make a raspy dack, dack sound. Pick them up and segregate them from one another and listen to their calls.
At 8 wks they look like females, mine just started getting green head and greyish chest a little bit ago and he's now 12 wks. I could tell by his voice at around 5 wks that he was a boy. Do they sound raspy or quack?
got some bad news 3 of the ducks an the blue orp chick in the pic are missing.there were no sign of the ducks but there was alot of chicken feathers.hopen the ducks might of gotten scared run off to hide we will have to wait an see if any come back.