One of the most common causes of rust stains on towels is iron in the water. When iron comes into contact with oxygen, it oxidizes and forms rust. This can happen even if you don't have well water; any time there's iron in the water, it can cause these stains. If you have hard water, there's a good chance that it contains high levels of iron. Another possible cause of rust stains is leaving damp towels in the laundry hamper or on the floor for too long. When towels are left wet, they're more likely to develop mold and mildew, which can also lead to rust stains.
If your towels have developed rust stains, don't despair! There are a few different ways to remove them. One option is to soak the towel in a solution of vinegar and water for 30 minutes. Then, wash the towel as usual using detergent and hot water. You can also try using lemon juice or baking soda; both of these ingredients are natural bleaches that can help remove rust stains. If all else fails, you can always bring the towel to a professional cleaner who will likely be able to get rid of those pesky rust stains for good!