The two reds you're using to AA are too similar to the dark red to actually soften the shadow or provide any impression of a lighter shadow in other areas, which means they're redundant. I think replacing the darker AA colour with the dark red and lightening the lighter AA colour across the whole image would make it look smoother, as well as avoid the banding you would've had if your AA didn't completely blend with the shadow.
Thanks for the feedback. I'll keep this in mind for my future works.