Hi,

There is a whitish, hardened discolouration at the bottom of the panels just in front of the rear wheels (including the rocker panels) and washing alone does not remove it. Any idea what it is and how I can remove it?

Thanks.

 

it's problem on vernis, you need make one paint.

 

That looks like road rash, but if it's some type of foreign material stuck to your paint, try a clay bar and then an orbital polisher w/ a light compound. If you're not a detailer, bring it to a local detail shop for an estimate. Good luck!