"Femmenized" seeds are NO guarantee of females.
environment early in veg' can play a roll in male to female ratio from seeds as well.( i.e. you can increase the probability of females from 'regular' seeds, through certain environmental factors)
http://www.marijuanapassion.com/forum/showthread.php?t=21546
Clones of plants that 'have' hermied, have the "exact" same propensity as the donors. It IS genetic. If slight or even "not so" slight stress induced staminate flowers in the mothers, "so goes" the cuttings/clones.
Cuttings from a quality, stable, female will be female every time. No need to buy "more" expensive, feminized seeds, no worry of hermies..:confused2: