Male Flowers with pollen?

Hi, I have a couple of very strong looking male plants, and was hoping to get some pollen from them to produce some seeds for the future (plan b if you like). However, my buds finally split open to reveal a flower with stamen, but no pollen?!? The balls started a few weeks back, and they've been under normal lighting (I'm growing from the sun) which is currently about 15/11. Could this just be the first couple of flowers being too eager and opening with no pollen, or are these weirdo sterile plants or something?

Take a bit of black construction paper or fine cloth and touch it to the underside of a male flower that has opened.
You should get some pale yellow dust. Just keep trying; you're more likely to snag some pollen if you get the flowers JUST as they open- catch it on the end of a Q-tip and use that to pollinate a few low buds on the females, and tag those buds with string so you know which have the seeds in them later.