DO NOT ADD CHLORINE!!

The turbidity is most likely a combination of planktonic algae and the rock dust from the pea gravel. You have what is called 'New Pond Syndrome' and the 2 inches of rain has exacerbated it be not only washing the dust from the pea gravel but most likely caused some run-off from the surrounding land raising the nutrient levels of the water column.

Aeration is always a good choice.

The problem should clear over time.