Lost in a SOG is correct, high N. It's getting to be fairly common knowledge that too much N late in flowering is one of the best ways to cause hermies. Those of us who practice N starving hardly ever see them. I have at least 4 heirloom clones that are known hermies. None of them have ever shown a hermie flower in over 10 years in my care, probably because I N starve. Of course there is a genetic component to hermie-ism as well. Some will be no matter what you do. Same with foxtailing. It's a mix of things like excess heat, excess N and genetics all playing together.
"My dream is a five pounder at the end of every cul de sac in the land!" Mr. Greengenes