Pistons? WTF!?
If it's yellowish and somewhat banana shaped, your plant has turned hermaphrodite on you. I don't see it in your photo either, but if you see it and from your description, you are the (not so) proud father of a shemale. If you have other plants nearby I suggest you move the hermie to prevent it from pollenating your other plants. If it's your only one, you can grow it out for some seedy bud. Keep in mind that your flowering period will be substantially longer as the bulk of the plant's energy will now go to seed production rather than flower development.