Stains in my vinyl lined pool

My pool was stained when I opened it. I have raised my PH and shocked to clear up the water. I can take a vitamin C tablet and it will remove the stains. I can't remember if this means metalic or organic stains. Please advise me as to how to remove them and keep them out. My pool 16x32 inground vinyl lined and holds 18,000 gallons. I am using Borax and Bleach and have a DE filter. Are there other sources for the chemicals other than a pool store?

Thanks for your help, Marty

I did a stain treatment with ascorbic acid followed by a sequestering agent like I have read. It did a great job. I backwashed my filter, and slowly raised my chlorine level with bleach and a couple of pucks in my feeder. My Ph only dropped slightly, and I added a little borax. Now about 2 weeks later I can see the white areas of my liner, ladder treads and fittings beginning to turn brown again. Do I need to add more sequestering agent? If I do and the stains do not go away, can I add more ascorbic acid? I have not added any water. I can't figure out where the metals are coming from. I had no trouble in the last couple of years. Here are my latest readings: FC 1.5, CC .5, TC 1.5, PH 7.4, ALK 70, CAL 30, CYA 80, TEMP 85. Please advise

Thanks, Marty

If vitamin C removes it I would say from all I've read here that it's metals.

Read this thread that tells how to remove using ascorbic acid (vitamin c powder).
http://www.poolforum.com/pf2/showthread.php?t=1883

Do you have a heater?

I just replied to your other post. Yes I do have a heater.

Marty