Nutrient deficiencies/toxicities, heat stress, any environmental stress, severe root bound, over-watering or under watering, wrong PH, you name it. But, generally you really can't do anything to guarantee a female plant except buy feminized seeds.
your best bet would be just plant more than needed,,, and when there 8 to 12'' tall,go to 12/12 and sex them,,if you wont 5 total,,id plant 11,,sexing isnt hard you just gotta know what to look for..