Yesterday I phoned my water company. The man on the phone wasn't too helpful, he suggested that it was dish detergent residue !! I will ring him back and ask for an address to send a sample for analysis. In the meantime I have harvested the 1 plant scrog I had going which seemed to be quite healthy, and provided me with six and a half oz's which is normal for my 1 plant closet grows. I intend to change my style of grow from top fed recirculating in clay pebbles to drain to waste coco.