The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
The female spinners were most obvious and were entirely light tan, had bright yellow egg sacs, and two tails.
You are describing either Procloeon or Centroptilum. Both are closely related genera in the family Baetidae and go by many common names, including Tiny Sulfur Dun and Little Pale Quill. What kind of water were you fishing?
Does the hatch you see look pretty close to this?
Tough to say. I never saw a spinner, only duns