Do I need Private Label permission to repackage a product if I intend to alter the formula by adding additional ingredients?

I am intending to open my own massage clinic when I finish my training & licensing next spring. There is a certain massage oil company that I like but I want to either alter the fragrance slightly or add my own proprietary essential oil blends, botanicals, etc., to their products, then repackage them in my own bottles & brand labels. First, their formulas are not patented. Second, I am aware of the FDA cosmetic labeling laws of ingredients. Third, I am trained in the safe use of the additional ingredients. Because I am using their product(s) as a "base" which I want to improve--with my additions from 1%-40% of final product, altering it noticeably & therefore essentially turning it into new products no longer identifiable as the original brand products--is this legal? Thank you!