The quick answer - yes, they can hermie that fast - doesn't usually happen that quickly but it's sometimes really hard to identify a male preflower until it's really obvious... Man, I've been there before - with bagseed you never know what you'll get. You can try to cut the balls off, but really in the end you'll end up with a smoke that's not very potent and therefor could be a waster of time and resources, depending on what else you have growing. You also risk getting some missed pollen on your fems....

As I said, i've been in the same boat before and since switching to only feminized seeds, I haven't had to worry about that nearly as much.