90% better on differin, but what next?

Hey! My acne is 90% better on differin, wondering if I should add in Azelaic acid or good molecules discolouration serum next. The serum broke me out for a week, then I didn’t see much difference over the next 2 months. Azelaic acid, I didn’t see much difference in 1 month. Now need to decide which one to continue with & just feel stuck, but it will be one of those two. Any advice?