stains on vinyl liner

i have and have had since last year anyway, some very light gray stains in a # of areas on my vinyl..especially it seems in the deep end.so light it looks like dirt that just won't quite remove. they are not slimy at all..just look like sediment that won't pickup and don't seem to be getting bigger, but i thought i would try to remove them. i've read through some of the stuff here and was thinking about trying vitamin c powder, but read i should use sequesterant first? i have some scale and stain remover, but no vit c powder yet. should i give it a try and if so, how to apply (it's liquid)

thanks

ps- all chemical levels except cya are in the proper range. i had no cya so put some in a few days ago to stabilize the chlorine i was burning through..up until about a month ago, i was using stabilized pucks for regular chlorination and stabilized granulated chlorine in heavy doses to shock at startup. no other chems have been used or it seems have been required as the values on the test kit are good.

Try Mr. Clean Stain Eraser - works great, search for my detailed post about it and some of the rave reviews others have given after trying it.

Do they scrub off, or are they rough? It would also be a help if you could post a set of numbers, so we can see what may be going on.

they don't scrub off with a pool brush..don't know if they are rough..i'll try to get some # if the mr. clean stain eraser doesn't work. i'll try that first.