Stinky is spot on. If you saw say, overnight, this change in your plants, or maybe over 2-3 days, they probably are male flowers. Calyxs usually grow in a little smaller in the beginning, and don't really fatten up until the last few weeks of flower. I'm inclined at this point to say that you probably have a hermie there.

It's okay if the hermie pollinates itself, just keep in mind that those AREN'T the seeds you are after. Keep an eye on the flowers, and usually around 10 days or so after they appear, they will open. Once they open wind and that spreads the pollen to the females and then we get seeds. Pollen can travel FAR on the wind.

Once you see the male flowers open, that's when you go in and take as many of them from that hermie as you can get. Keep those tiny flowers/pollen in a container. If you can seperate the pollen from the flower material, do it. Usually done with a keif or pollen box. A simple silkscreen with glass under it would work. If you can't no biggie, i'm sure you can still get it to work.

You take that pollen to another healthy girl, not hermie, must be healthy female. Take a small paintbrush and "paint" the pollen onto the pistils of the healthy girl wherever you want the seeds to grow. Continue plant as normal and harvest seeds once the calyx breaks open and you can EASILY take the seeds out. Those should be femenized. No male DNA used to create them, just male pollen from a FEMALE plant that was stressed, and a healthy female.

BTW, if you want, after you harvest the pollen from the donor, you can spray it down with plain ole H2O. I have read that H2O will render cannabis pollen inert. So you can at least limit the damage somewhat.

Also, make sure the healthy female you want to seed has at minimum 4-5 weeks left to flower so you can get the seeds to finish fully.

I'll hang around and fill in anywhere I can. Keep in mind this is more of a synapsis then a step by step tutorial, but I think you'll grasp the concept.