We have a 'few' rust spots scattered over our liner that I noticed last summer. Vitamin C tablets worked on them. They are only noticeable whilst swimming around under the water with goggles on. I was thinking of doing the Ascorbic acid treatment right after opening the pool in 10 days or so, since the chlorine level with be pretty much 0. Is there any thing I'm not considering with this approach? I was going to run the ascorbic acid treatment and then bring the levels of everything up as usual.