You can use ascorbic acid (vitaminC). Bring your ph down to 7.2, crush some vitamin C tablets and put them in a sock. Rub them on the stains, the stains should go away. If you have a lot of stains you may want to purchase some ascorbic acid. Add some sequeserant, such as jack's magic, or metal free, or sequasol something that says it will get metal out. Sometimes just adding some sequesterant along with bringing down your ph, the stains will go away.