If he did not realize he had hermies until he finished flowering is that because they were not that bad and hard to spot (as in just started to hermie at end of run)? Or because he just simply was not paying attention? If his crop did not hermie till the end more than likely it was due to something he did to stress the plants out. I stressed out one of my crops before by changing nutrients during flower and had hermies pop up around week 4, i sprayed with Reverse and Saturator and was able to kill off all the bananas. However if it is genetic, Reverse may not work, or if it does, any clones taken from that crop will continue to hermie as well. Best bet is to just watch and hope he stressed his crop out. But if yours hermie as well I also advise getting rid of them after your run (if the Reverse works).