I have metal stains on my fiberglass pool steps & at the water line. I have citric acid to remove the stains. I have to drain approx. 1/2 of my pool water due to REALLY high CYA. Could I go ahead & treat for metal stains before draining my pool? I think stains came from rust on the ladder, which has been replaced. Should I add metal out after the citric acid & then drain the pool or wait until refill & then treat?