I haven't seen anything screaming "cockerel" but I'm used to sexing breeds with big single combs. 

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they dont have single combs?I haven't seen anything screaming "cockerel" but I'm used to sexing breeds with big single combs.![]()
I know each breed may be different, but by 6 weeks the eggs I hatched had pretty clearly differentiated. This is a cockerel Cream Legbar and Rhode Island Red hybrid at only 4 weeks. You can clearly see the development of comb and wattles. On the other hand, this six-week-old Rhode Island Red has some comb, but it is much smaller and yellow still. There's no real trace of wattles on her.
Like @3KillerBs, single combs are the only thing I've had to worry about. I can't tell if yours are different comb types, but assuming single combs they'd be safely pullets.