Here is the email reply I just received from Mardon MLC:
Hi Daniel,
That must be discoloration by the putty (bondo) in the joint area.
I just talked with my workers about it and they suggested using a 600 - 1000 grit sandpaper and sand the area where the discoloration is present.
The sandpaper will sand off the clear top coat. After that, paint the sanded area with basic white acrylic paint and when dry spray a clear top coat to protect your paint job & add shine to your helmet.
Mardon (MLC)