Any chance part was a brown bloom. We get those toward end of summer after no rain for a while. The only other thing I can think of would be that in renovating the pond you set the stage for some chemical event that would not occur until a certain water temp occurred for a period of time. Really guessing here. Is the aerator off the pond bottom? If the water volume in the pond went down some that would increase the water turnover rate via aeration which in turn could add to turbidity suspension.