Suddenly seeing a few rashes. Could it be the vitamins I'm taking?

I'm currently taking the following to supplement my weight lifting- Preworkout: B complex(energy) and flax seed oil(vitamin absorbtion). Before bed: Acidophilus(all around digestion), zinc(testosterone), multivitamin, biotin(skin), potassium gluconate (why not) flax seed oil(absorbtion). What could be causing these rashes? I'm seeing them above my chest on both sides, one in the crock of my arm, and one starting on my left bicep area. I'm assuming it's vitamin related...but before I just stop taking vitamins and slowly route out the problem vitamin, can anyone point out a possible culprit?