Pullet or hatchery roo boo boo?

[buttercup hill]

My 5 Buttercups will be 4 weeks old tomorrow. They're supposed to be all pullets but one of them has a red comb already (first photo) while the other 4 still have tiny pink nubbys (second photo).
If this one is a little roo, is this kind of mixup normal from hatcheries? I mean, does it it happen very often? Any input would be appreciated. This is all new to me.

 

[speckledhen]

Looks like a sexing mistake to me, yes. Sexing is an art and not 100% accurate.

 

[buttercup hill]

Aw geez, I was afraid of that. Well, at least he's a cute lil' bugger. I'll be watching my brown leghorns now since they are to be pullets, too. Thank you!