Chest/back breakouts - what's causing them? (photos)

I've gotten small breakouts on my chest recently, and I've had some on my back too (only realized a few weeks ago, could have been there longer though). I also have some dark marks and reddish-brown bumps on my back and butt from improper shaving (at least 4-5 months). I started using amlactin and neutrogena body acne body wash today- is this an appropriate routine to follow? Do I maybe have something else (folliculitis/KP)? The bumps are not itchy or painful and I have no history of acne.

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