In a large mixing bowl, combine the sourdough starter, filtered water, and dill pickle brine; mix until fully combined. Add the bread flour, whole wheat flour, and sea salt to the liquid; mix until a shaggy dough forms. Cover the bowl and let the dough rest for 30 minutes to autolyse. Add the chopped dill pickles and fresh dill to the dough; fold them gently into the dough until evenly distributed. Perform a series of stretch and folds every 30 minutes for 2 hours to develop gluten. Cover the dough and let it ferment at room temperature until it has increased by about 50% in size, approximately 4-6 hours. Shape the dough into a boule and place it into a floured proofing basket; cover and refrigerate overnight. Preheat the oven to 475°F (245°C) with a Dutch oven inside. Remove the dough from the fridge and carefully invert it onto parchment paper. Score the top of the dough with a sharp knife or razor blade. Carefully place the dough with parchment paper into the hot Dutch oven; cover and bake for 20 minutes. Remove the lid and bake for an additional 20 minutes or until the crust is deep golden brown. Allow the bread to cool completely on a wire rack before slicing and serving.