I currently have the same problem. What it is, is that not all feminized strains are stable. I purchased The Church from Greenhouse Seeds and that is one of them... it cost me $5 a seed, no wonder. To make a feminized seed you do all of these things that essentially stress a female plant hermie. So unless the seedbank/breeders have stabilized the strain to no longer be hermie (there are good feminized strains out there), the plant is highly likely to be hermie just as its genetics are. What I do is use my thumb to rub off all of the seed balls. Of course you'll have plenty of obvious bud sites, so you need to look for the seed spots... they're very small. Check out my Church plant that went hermie recently, also under a 600watt HPS: