If you check your plants everyday which for most smaller grows I'm sure you do you really do not have to worry about not finding a male plant it is going to show it's sex eventually and when it does you will clearly know male plants will just pop balls out fast as shit at least the ones I have found happened within 24 hrs one day they looked normal the next male plants. You do have time no need rush sexing them. Are you letting them mature or did you flip to flower? If you flipped to flower just keep checking on them daily. If you are letting them mature you really have nothing to worry about until the females start to flower as long as you keep a clean grow area. Just my opinion and you know what they say opinions are like assholes everyone's got one lol.