I was able to remove stains from my overflow hot tub by pouring in a couple gallons of acid and letting it sit for a few hours before neutralizing it and mixing back with the main pool. However, I may have overdone it. Now the gem coat from Florida Stucco is rough and comes off when brushing. There is a small pile of the coating (looks like sand) at the bottom. Is there anything I can do to make it smooth? Will it eventually stop coming off? Should I brush with a stainless steel brush, or stick with plastic bristles? Or should I have the entire thing re-done? Its only 6 years old.