Its generally fine to eat, and youre right its the acid.

I am making lasagne. Put in my last ingredient, Muir Glen tomato puree, and noticed only after that there are small spots in the can. Can has an expiry of March 2024 so it's clearly been around for a while. It's as if some of the acid wore off the lining along the seam (fully brown) and in spots, so rather than the orange lining one sees brown spots. When I run my finger over them, one can feel the texture difference. Unfortunately, forgoing means trashing my lasagne ingredients amd starting over. DH thinks it's fine but from what I read this could be rust in the can, which is not safe to eat. (The can is not dented or bulging or anything like that.)