We safely removed our popcorn ceiling in hopes of have a loft-style exposed concrete look. We also sanded the ceiling with 40 grit paper and wiped it several times with a wet cloth. We now have these swirly white stains that we can't get rid of.

A friend suggested painting the concrete a dark grey colour, my concern with painting is that we will be covering the texture of concrete. Any suggestions to how we can clean the stains without painting?

Thanks in advance for your help