Female Leucrocuta hebe (Little Yellow Quill) Mayfly Dun Pictures

Haven't checked any keys to verify, but most of the little late-season Cahill-looking duns are Leucrocuta. If I had to guess at the species, I'd say hebe (Little Yellow Quill). It is probably the most common L. spp. in the East and has a long hatching period that extends well into the fall.

I would also agree that the spinner you photographed is the same species.