Liner Discoloration

I removed my winter cover and found that certain parts of my vinyl liner are heavily discolored. All discoloration seems to be at the top of the vertial posts and are well above the current water level. It doesnt occur in between the posts. Its a yellow discoloration. Could this be caused by adding too much bleech during closing? Does this mean the liner is shot? I tried adding a picture but couldnt figure it out.

Could really use some help here.
Thanks
John

Most likely bleached it out.

I was thinking of that but why would it only be at the top of the vertical posts and not between them and above the water line?
Thanks
John