Went out after work today on an upper stretch of valley and notice a blueish tint in the water I've never seen. As I made my way to a spot that usually holds I noticed a whitish belly of a dead fish. As I looked more I saw another and another. I walked further down and white bellies everywhere. Some fish barley kicking in circles. It was one of the most disheartening things I've ever seen. What could have caused this?