Smoking motor mounts?

I have Lord motor mounts and I've noticed something odd after about 40 hours. The mounts have discolored the engine mount just along the top of the Lord rubber mounts. I'm thinking on start up and shut down they move just enough to heat up and burn some rubber. Wondering if they're tight enough or maybe just their nature.

I too see discoloration of the engine mount powder coating in the area around the rubber mounts. I also see it around all the rubber cushioned clamps (adel clamps) that I have on the engine mount tubes. And I haven't even fired up the engine yet! So whatever is happening to cause the discoloration doesn't seem to be vibration or heat related. It seems that just the presence of rubber in close proximity to the powder coating causes that discoloration over time. Maybe a chemist among us could offer an explanation?

Same as tires sitting on an epoxy floor in a hangar. Chemical reaction in the powder from the rubber.