Drain your pool by following your manufacturer's guide. It is much more effective if it's drain. Other cleaning products claim that they can clean all the stains while there is pool water but none have proven to work.
Remove your stained Oval Heavy Gauge Metal Diamond Uni-bead Liner but be sure to collect all the liner clips.
Spread the liner on a surface that has no nails, rocks, and other debris that could puncture it. Mix one part bleach to two parts hot water. Sponge the stained area and if the stain doesn't remove, consider adding little more bleach. Leave it for about ten to 15 minutes. Repeat the process if needed.
Use plastic buckets filled with water. Place the liner's edge on it.

Use only soft synthetic scrub that is specially made for swimming pool and liner for brushing. Other brush could damage your precious liner.
Use paper towels or clean towel to dry the liner.
Carefully install your liner.