My Adidas Shoes Turned Yellow After 3 Months and Were Not Replaced

I bought Forum Low shoes from adidas, and after just 3–4 months of use, yellowing started to appear on the front of the shoes. I take good care of my shoes and wear them under normal conditions, so this kind of defect is unacceptable. I requested an inspection, but the shoes were not replaced. In the rejection letter, they made me look like a liar, claiming the issue was due to usage. However, the same problem exists in other adidas models as well, which clearly shows it’s a product flaw, not user error. I want a solution to this. Adidas is a huge brand, but the way they treat customers is disappointing.