I have read about and thought over hermies a lot. I'm not a botanist, but I play one in my garden. This is my semi-educated opinion and is part speculation. Caveat emptor:
Almost all cannabis plants have the capacity to become hermaphrodite. This is a survival trait. In these plants, as in all, the primary objective is to reproduce. Everything else is secondary to these girls. A female seed will grow to be a female plant, and will mature and bloom. If it is pollinated by a nearby male, it will reproduce, creating seeds that share the genetics of both parents. Then the plant dies. They all die every winter in the wild. The seeds they produce are their only method of insuring that cannabis plants will be standing the next year.
If it does not get pollinated, the cannabis plant will react to this. Pollinating a single flower causes that flower to change and produce an embryo. In the process it sends chemical signals to the surrounding plant, which then supports that flower and it's embryo instead of starting so many new flowers. But if it is not pollinated, the surrounding tissues keep doing what they have been doing: making more flowers.
This is the best reason why we grow sensimilla or unpollinated females. Sure, it's nice to get the seeds out of your smoking buds. But because none of them steal resources to grow seeds, they make more flowers. That means bigger, denser buds.
So the plant naturally plays the numbers. But that is not the only way it can combat a lack of pollen in the air. It can also hermie. Sure, there are genetic issues with self-pollination, but in the short term it is clearly better than dying without reproducing.
I am unsure of the real mechanism for triggering hermies, but I have a theory. I believe that nearly everything in the plant happens because of hormones. I think that when a male flowers, it does so because it is producing a mix of hormones that cause that growth. When a female flowers, she produces a different mixture of hormones, producing female flowers instead. These hormone mixes may not be the same, but they may have overlap.
I suspect that if the production of hormones is not exactly matched to the usage some will build up and others will often be short. This leads to variations in how different strains express their sexuality, and probably every other observable feature of the plant as well. I speculate that as a plant produces the hormones, they vary in that mix from strain to strain, meaning some will tend to over-produce some hormones, and others over-produce a different set of hormones. The closer that over-production resembles a male hormone mix, the more likely a given female node will react and become male. As a plant continues to bloom, the imbalances will get greater and greater, making it more likely that the plant will exceed the threshold in one or more flowers and hermie.
All stresses are simply conditions that cause the plant to react to preserve itself. These reactions are due to hormones that are affected by the conditions at hand. They modify the production of hormones and can therefore also lead to a buildup of hormones that will be expressed as male flowers.
So to summarize: The tendency to hermie is a survival trait; a way for the plant to continue it's genetics. Different strains vary in their exact hormone production. Excesses due to stress or natural variation in the mixture of hormones naturally produced can lead to male flowers over time.
Now acquired traits are not passed on. This is basic biology. Only genetic traits can pass from generation to generation. So if you torture a plant until it hermies and then pollinate it with it's own pollen (like when making feminized seed), the offspring will not be more likely to hermie as a result, just as your child won't be born with a broken arm just because you had one when you conceived the child. The tendency to hermie - given constant and consistent conditions - will be unchanged by selfing like that because there is no change in the genetics (other than mutations, but we can leave that out of the conversation because that is a relative rarity). So feminized seeds should not increase the likelihood of going hermie just because they were selfed. At least no more than any other random genetic mistake (mutation).
Changes in external conditions and internal processes can however. If you stress them, some strains will hermie very easily. If you cross that strain with another that hermies easier, the result might be a hermie nightmare. Or maybe not, since there is some randomness to what traits are passed by which parent. Other strains are harder to stress, meaning less likely to hermie. Some at the extreme require the direct application of hormone to force the issue and would otherwise never hermie. In the wild, strains with this trait would fail to compete and disappear from the gene pool. Here on 420mag we do everything we can to fight that survival trait. In breeding for that we make the plant more dependent on manual cultivation to survive.
That's what we call domestication and one of many reasons why we should all be concerned about the preservation of pure landraces.
I would not assume that this one hermie is alone though.
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and 
brodda. Gonna do my best. Hopefully they put on a decent show for us.
