I have an old basement set stone fireplace. Due to a moisture issue, the stones started to have efflorescence show up. We repaired the moisture issue but we could not remove all the of salts from the stone. It was recommended to me to etch the stone to remove the efflorescence which it did but the dissolved salts have left white streaks in the large grout areas around the stones. How do I fix the white streaks in the gout?