Roosters pretending to be hens

Here goes. I know this sounds weird. And maybe you'll think I'm silly or stupid or both. But there are three "hens" in my flock of 16 birds who are actually roosters. At least, they definitely WERE male. They are now camouflaged as hens. I want to dispatch them, as I'm not keen on feeding three birds that are not laying eggs and there are enough of them in the chook shed... but the problem is, I can't tell them apart from the hens, so I might not be dispatching the right birds!

That's the short story. The longer version is this. Of the last little batch of four Barnevelder chicks hatched back in March, unfortunately three turned out to be male. They were clearly boys - stood taller, had thicker yellower legs, their combs developed quicker. When they outgrew their little chook tractor, I didn't want to move the girl in with the older birds on her own, as she was smaller and I thought she would get picked on. Chooks are nasty that way. So I decided to move all four young birds in with the flock, where they pretty much kept to themselves and seemed to get on fine.

A couple of weeks later, I passed the chook shed on my early morning walk and heard one of the young cockerels trying out his (kind of pathetic) crow. I remember thinking, "I'll have to catch and dispatch those boys soon before they cause trouble." Then I was away for work, and we had some atrocious weather... no time to spend my weekend butchering birds for the freezer. But in the few weeks I delayed, the three young lads stopped looking like lads and I couldn't tell them apart from the Barnevelder hens! Every now and then I think, that one's comb looks particularly red, or that one has a tinge of green in its feathers. Then I look around and see a bunch of other chooks that look just the same. And at night, high up on their perch, there is just no way I can tell them apart with enough confidence to kill them. We have one mature rooster, Vladimir Putin, and my only guess is that to avoid his wrath they are somehow pretending to be hens. Seriously, they do not have thicker yellow legs, spurs, large combs or colourful rooster plumage at all.

A Google search revealed quite a few stories of hens who have turned into roosters, like Gertie who became Bertie. But not so much about spontaneous sex reversal the other way around, such as Gianni the cockerel who started to lay eggs. I'm starting to think I'm going crazy! Any chook experts out there ever seen this before?