I have a Stonescapes plaster pool, 25,000 gallons and coming up to the 4th summer of ownership. I had a neighbor child throw rocks into the pool over the winter time. I didn't check the pool for almost a week and then I looked outside and saw a big rock on the deck and went outside to find two rocks on the bottom of the pool. They left two stains. I have tried to leave chlorine pucks on the stain to no avail. I just tried putting Vitamin C tablets on the stains. It was a no go on that one too. I have always maintained the pool at TC 4-7 and pH from 7.8 to 7.5. So the question is, will shocking the pool and keeping the chlorine high get rid of the stains? Any thoughts on what I need to do?
My current readings are:
Here's a pic of what I'm seeing: