Good morning,

I believe you actually have powdery mildew, the white and gray fungal growth on the leaves are tell-tale signs of the disease. Typically, we see this disease when we have: high relative humidity at night, low relative humidity during day and 70-80F temperatures.  

I wouldn't discard your garden soil since these spores are prevalent in most soils. Instead, practice good sanitation, crop rotation, plant spacing recommendations and irrigate in the morning at the base of the plant versus overhead watering. 

Try to keep turning your compost pile weekly to encourage the litter to break down more quickly. Powdery mildew (and Downy) can be a natural part of desiccation in humid environments. 

Here are a few resources: 

Backyard Composting - Alabama Cooperative Extension System (aces.edu)

Common Landscape Diseases in Georgia | UGA Cooperative Extension

Backyard Composting Tips - Alabama Cooperative Extension System (aces.edu)

Controlling Powdery Mildew on Ornamentals - Alabama Cooperative Extension System (aces.edu)

Let us know if you have any additional questions!