Can I use Retin A 0.5% with a cream containing Kojic acid and Vit C together at night?

These ingredients can be used simultaneously. They target different things. While Retin-A helps to shed the superficial skin layers and stimulate collagen growth, kojic acid helps to lighten the skin and smooth out pigment irregularities. The Vitamin C also stimulates some collagen growth but also acts as an anti-oxidant and moisturizer.