Retinoic acid cream, moisturizer, and a bleaching cream

My derm prescribed me these topical meds(in order) antibacterial toner, moisturizer, retinoic cream, tyrosinase inhibitor cream. I have moderate acne, though i did purge a lot at the beginning of my treatment, i am in my 6th week now. How long should i wait in between applying my meds? i am currently treatin all PIH from my purging. Will retinoic acid help fade PIH? Is it necessary for these dark spots to flake off or it will just fade with continuous use?

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