I had this exact issue, the dry water stain-looking marks not going away no matter what. I took it to my dealer and they said a process was left out of its preperation from when it got shipped over here. That there was some sort of layer on the paint that aws causing this to happen. So my dealer got this removed and ever since it has gone.
So it may be worth you taking this up with your dealer, worked for me
Also your MiTo is Etna black too so it may be a common problem (or laziness) amongst Etna black ones..