3 inch white ring around entire pool vinyl linef

Just dropping water lever prior to putting cover on for winter and noticed my entire pool had this white haze around pool at the height of my fluctuating water level for the summer. Liner is 2 years old only my second in 19 years. I keep pretty tight control on my numbers. When I examined the white it had no texture felt same as vinyl and not greasy. If I scratch at it with my finger nail it does slowly come off. Tooth brush or other brushes don’t touch it. Tried 5% vinegar may of helped a bit. Wanted to try magic eraser but read not to. Any suggestions would be appreciated. I’m holding off on closing for winter until I remove this stuff.
28k gallon vinyl
Current ph 7.6
Free chlorine 4
Alk 40ppm
Ca hardness 200 ppm
Cya 30
Salt 3200ppm
Test kit K-2006