Filtration lines will always come back unless you seal the gap under the wall. Sometimes more aggressive cleaning leaves more residue causing them to get worse.the 1st time cleaning my original pic place, mixed up extra strong boosted prespray, hand agitated the lines with microfibre rinsed and dry stroked it to death and it looked great.. but 8 months later da-da we're back! I think it annoys me more than the owner