This time of year, my guess is they were eating bwos. Did you try any of those patterns? Pheasant tails usually work for bwos, but some of the other flies are absolutely killer (and more accurate looking IMO), like barrs bwo for instance
Did you try to "crash the hatch"? Sometimes throwing a big ugly streamer or big bushy attractor dry will induce a take.
By far I've caught more fish on bwos than anything else there, but usually it's on the surface.