I don't think it is algae either. It held the chlorine shock level over night, so I think it is like you said and must be something falling off of the trees.
There are two large maple trees close by the pool. I think I need to have them trimmed way back this fall. We are also having an unusually dry season here in Tennessee, I am constantly battling leaves this year. Something that I never have to do until that fall.
Thanks