Now maybe I'm just a devil's advocate, but I'm going to argue male. Yes, barred Plymouth Rocks are one of those breeds that are apparently very easy to sex due to colouration and all that, but I've had experience with quite a number of chickens that have their combs and wattles explode in, but don't get saddle feathers, sickle feathers, or pointy neck feathers, or even start crowing until they're nine or ten months old! My boy, 3/4 Rhode Island Red 1/4 barred Plymouth Rock, didn't start crowing until he was about seven months old and his two brothers didn't follow suit until they were nine and ten months old - but, I spend a lot of time with my boys and make sure they feel very comfortable and happy. Bo, my boy, gained all of his rooster-y qualities, feather-wise, very early, whereas it took his brothers quite awhile to follow suit. Jules didn't start looking like a rooster until he was ten months old! No spurs, no pointy feathers, hen-tailed, and all that. Their father was the same way.
My indication that this would be a boy is to look at everyone else's combs and wattles - they're tiny and still a pale pinkish colour! However, you say the comb and wattles seemed to "come out of nowhere" which is a much more hennish quality, since ALL my boys, regardless of how long it took them to start crowing or growing in distinguishing feathers, began growing in noticeably larger combs and wattles at about three or four weeks of age, but I don't often see girls with quite that large of combs and wattles.
In short, your chicken there could go either way, but my experience says boy. Then again, my experience with Plymouth Rocks is in mixed-breeds and a bundle of chicks I've been watching develop in my house mate's flock. Good luck, and lots of love always goes a long way, even with your boys. :3