http://piscines-apollo.com/docs/chemicals_and_vinyl.pdf

Basically if the liner is discolored it means too much chlorine, if it's wrinkled it means pH too low. pH is what kills liners. The calcium content is dissolved and the liner swells up and wrinkles. Water with high chlorine concentration can then penetrate further into the liner. The liner loses its elasticity, it elongates etc, we've all seen it.