It could also be partial mixing of the water in and just above the thermocline or bottom sediments. Any recent fairly strong winds or weather fronts to circulate the pond? I noticed the three water temp zones are now closer in temperature. Thus top, mid, and bottom have similar density and less resistance to mixing. Mixing, depending of strength, not only circulated nutrients for plankton growth but also fine micro sized detritus. Fall naturally stimulated lesser phytoplankton blooms are common in temperate waters.
On your mixing question, "Any recent fairly strong winds or weather fronts to circulate the pond?".
The weather has been pretty benign in the wind department. We did have 2 inches of rain in our area the previous week. That rain and the runoff into the Rock River caused the pond to rise about 5 inches from the previous week. That certainly could have "lifted" some bottom sediment into suspension.
Since there would be little resistance to mixing because of the like water temperatures top to bottom, the combination (of lifting and mixing) could well be factors in the drop in clarity.
