I have the same issue also I went to pick up my bf and noticed the same spot on the a-pillar also. I already contacted GM Customer service. I already had a leak I the trunk, dealer said it was from the spoiler they ordered a new spoiler resealed it and haven't had a problem with the trunk since besides a bolt or screw they lost between the outer and inner skin of the trunk (Going Monday to resolve this). Since I got the car back from the leaky trunk and not even 2 weeks later I have this problem now. Its like every month there is a issue with this car or take one step forward and two back. I am so upset, this should not be happening with a brand new car that's 6 months old. I will be uploading a video tomorrow of this issue. Maybe someone can help me out