any more suggestions for back/chest acne?

I need your suggestions please-

I am a healthy 27 y/o female.
I am 15yrs vegan, I eat almost no sugar, I exercise 3x a week, I only use organic, natural 'soaps' to wash my clothes and my body, I take organic multi-vitamins & pro-biotics, I get 2x annual colonics, I do yearly parasite cleanses, I take a tablespoon of flax oil daily, I take no prescription drugs, sometimes I even use the detox foot patches.

My face is bright & clear & glowing, but I have terrible chest & back acne. My upper back especially. Does any one with experience have any idea why my Acne would be localized to these areas? Any help at all would be so much appreciated.