First, prune away and discard ant affected leaves and clear any fallen leaves and plant part form below the plants. Feed them right away with Espoma Holly-tone organic food. Make sure any sprinkler systems are NOT spraying the plants with water. Start a preventative spraying program with a sulfur or copper fungicide. Nutrition and hygiene can go a long way to preventing leaf spot in the future but the fungicide spray may be need to get it under control.