You might consider adding some washing soda which, when used as a laundry aid, helps to break down grease stains. It will raise your pH and the TA, depending on how much you put in, but it won't hurt the water. You could also see if your local pool store(s) carry an item called 'sum ball' or 'scum bug' which is a sponge-like thing that sits in the filter and catches body oils, suntan lotions, hair conditioner and such. Keep the filter running.