Bought a house in July last year that the previous owners did not maintain, I've been trying to get rid of staining for a while now with no luck the stains are yellow brownish and some are black, tried spot out and shocking. The pool store told me try drain free acid wash with two gallons of acid. The water test is normal except the TDS are at 4400. What are my options? I have pictures I can post and we live in central Florida