The answer to 'why is my stone walkway brown patches' is that the most common causes are dirt buildup, mold/mildew growth, and weathering. Over time, dirt and debris can accumulate on the surface of stone pavers, creating unsightly brown or discolored patches. Additionally, moisture and lack of proper cleaning can lead to the growth of mold or mildew, which can also cause discoloration.
To address this issue, you'll want to thoroughly clean the stone walkway using a mild detergent or stone cleaner. You may also need to use a stiff-bristle brush or pressure washer to scrub away any built-up grime. If the discoloration is due to mold or mildew, you may need to use a specialized mold and mildew remover. In some cases, the walkway may need to be resealed to protect it from future weathering and staining.