Hi all. I'm new to this site but found it to be very useful. I'm having issues with brown smudges on the wall/floor of my pool. I've tried shocking the pool, brushing with brush, brushing with chlorine tab, and also vitamin C tablet to no avail. All my levels are in perfect range and were checked 2 days ago at Pinch a Penny. I've attached pics of what i see. Any help will be appreciated.
I have a 10k gallon in-ground gunite pool. Not sure of pump size. Levels are normal.