Clear Water Yellow liner

[CBLA1956]

Opened pool did all the usual opening procedures. Have done same procedures since 1994. This year after opening the pool within a day the walls seem yellow as if they are stained. Have vacuumed on waste, used chlorine, shock, algacide etc. Tried brushing walls which does not phase it.
Does anyone know what is causing this? And what should we do to correct it. Chemicals are balanced. Have increased chlorine level. I would appreciate any input on this subject.

[Buggsw]

Could be iron in the water. Try crushing some vitamin c tablets in a sock and rubbing in an inconspicuous spot. If it lifts the stain, it's a metal stain