Slab Staining Help

[CDF-CW]

A customer of mine has asked if we could pressure wash her patio. We’re relatively new to the pressure washing game so haven’t come across marks/staining like this before. Any go to solutions for this sort of staining? Any assistance would be much appreciated

 

[K in Kent]

The 1 on the left looks a little like efflorescensce but I'm not sure it is. Has it been sealed before?
Try wetting the slabs and see if the stain goes temporarily