I couldn't believe that the fly choice was the problem but this fish struck on the very first cast after putting on a bright yellow Coney Leech. The lake is only 10 feet deep and I was fishing the dropoff as deep as I could get the fly. The surface temperature had risen 4 degrees to 76F in just a couple of days so they were likely holding as deep as they can, perhaps where there is a spring. There isn't much O2 in 76F water so even bass avoid it if they can. For trout that is near fatal temperature which is why I'm still fishing bass and not trout.
The forecast is for a cool latter August so I may be trout hunting sooner than usual. I don't mind this weather at all!