WE do exactly the same paul,the dust/pollen is too fine to filter.One thing that did improve things was to strim the land around the pool.This reduces pollen and insects.The sun cream tends to leave a scum mark around the waters edge.This can be removed carefully by lowering the water level and cleaning it with solvent.It seems it's the only thing that will dissolve the oily substance.The chlorine tablets tend to dissolve quicker as the temperature rises.
We have had no problem with discolouration other than the dust and pollen.This usually settles after 2 or 3 days of non use and can be then 'vacuumed'off as above.