KJN . . . sounds to me like you use one particular method of fishing for Smallies that doesn't work as well in September (topwater? Fast retrieve? 'white water' only?) as it does earlier in the season? I assure you that September is one of the BEST months for Smallies. While they do go low n' slow as the water gets colder, those who target them will not be disappointed. Echo everything that all said. No bad water for them in the Allegheny River watershed. All about water color/depth right now . . . either Allegheny OR French.
I'm stuck in southcentral PA now, so don't have access to my homeland. If I did, you wouldn't catch me near Erie Steelie tribs until Spring. Too much action in Allegheny shed w/ Smallies, Walleye, Musky, Pike, and Fall 'River Run' Trout to combat fish up on Lk. Erie.
Good luck!