I see the one blossom you refer to.

Without doing some research online the only thing I can think of offhand is that the blossom has not been self pollenized and is about to fall off where the pedicle is. Another possible reason is too much rain causing rotting of the stigma atop the style.

Do either of those make sense to you as in how many other blossoms are showing the same symptoms and have you had lots of rainy weather lately?

Carolyn