[trees]

Need some help and advice from you lovely people. Pressure washed an area and all was lovely and clean when  left. Now 3 months later as it begins to age/ get dirty again there seems to be lines appearing ? The person used a flat surface cleaner with a 21lpm machine no chemicals were used. Are the marks due to user error of the flat surface cleaner or even a problem with it? . Would it be beneficial to try a chemical solution on this? is this caused by user error?

thanks in advance