The answer to 'why is my gutter stained' is that gutters can become stained for several common reasons, including debris buildup, algae growth, and mineral deposits. Stains in your gutters are often a sign that they need to be cleaned and maintained.
One of the most common causes of gutter stains is the accumulation of leaves, twigs, and other organic matter. As this debris sits in the gutters, it can decompose and leave behind unsightly stains. Additionally, moisture and standing water in the gutters can promote the growth of algae, which can also lead to staining.