That will depend on how the seed was created. I think a "Feminized" plant as you put it, is a normal plant. If the same plant is producing single male flowers and fertilizing itself then the seeds will be XX (as I understand it).

If you have hundreds of fully mature looking seeds then where did the male pollen come from?

Have you tried sprouting any since you posted?

If they are real BB seeds they should be valuable.

The real question is "Who is boffing my girls?"