Have you tried wiping it with a slightly damp cloth?
I'm having a hard time seeing the spots. Could it be the print rubbing off? This does happen with DE.
My speedy b 25 in de has that on all 4 corners and I even was super careful. I was told its normal and that if it rubs against things it can rub the lighter printing off
Same with my Speedy B 30. I have a ZCW also and afraid this will eventually happen too it. From my research, and looking at used DE SLGs pics they eventually have this dark rubbing issue. Thinking of selling the wallet and getting only mono SLGs from now on. Still love my Speedy B 30.