The answer to 'stone walkway brown patches' is that they are commonly caused by a buildup of organic matter, moss, or fungus growth on the stones. Symptoms include discolored, patchy areas on the walkway that can make the surface look uneven and unattractive. To solve this problem, you'll need to clean and treat the affected areas.
For minor cases, you can try DIY solutions like scrubbing the stones with a stiff-bristle brush and a mild detergent or bleach solution. More severe cases may require professional power washing or applying specialized stone cleaners and sealants to prevent future growth.