My pool 18 x 36 inground is currently having brown sediment buildup or mustard algae as I get ready to close. Added Yellow out and one other algecide for brown black, green, and yellow algae. I actually have replaced the filter and 300# sand. Also added non-chlorine shock. Getting ready to close pool added 2 qts of winter algecide, the shock, and metal out .... Still showing signs of buildup on bottom of pool !! Any thoughts ??