I started using CRS 15% Vitamin C 2 a week a.m.to brighten my skin, while on Retin-A.My skin felt a tiny bit stinging and redness upon application. But later in the day, my skin had few tiny red itchy bumps that turned into tiny pus-filled pimples. I patch tested my neck skin & didn’t have this reaction. Is it important to have Vitamin C serum? Is there a next best Vitamin C serum that is less irritating than L-ascorbic acid, while providing some skin brightening/anti-aging benefit?