I'd like to be the one with the answer but that has happened to me also. In salt water we referred to some places where this happened as feeding stations. A certain part of the tide would produce like gangbusters and then somebody throws a switch and you can't buy a bite. As I got to understand this I moved with the tide and found fish a bit further down the tide at another station. Could they be moving down a dropoff maybe or into deeper water for some reason? Just my two cents worth.
Creativity is just intelligence fooling around