The hermie can happen when the plant is stressed or forced to think that winter is coming before it is ready to flower. if the light hours change before pre-flower, then the plant is forced into a last minute rush to make seeds, considering if it were to happen in the wild, it would mean that most of the males would have already released their pollen. the plant goes hermie so that it can pollinate itself in a last resort attempt to reproduce. Good luck with those plants.