[Acne] Targeted Shoulder/Upper Arm Acne - Any Advice?

I'm a 27 year old male that has relatively acne free skin on my face, but I seem to continue to have red acne/bumps along my shoulders and upper arms. Outside of the occasional pimple on my back, this is really the main skin issue I have. They seem to get worse when I'm in the heat or working out. I have relatively oily skin, but I don't do much beyond shower 2x a day. Does anyone have any similar experiences or ideas for what to try? I went through the beginner routine, but it seems that is primarily for face stuff and I didn't know if there was a difference in my situation.

I put some photos here for context https://imgur.com/a/wKKiv