Face getting darker than neck with exfoliation (tretinoin) in Indian skin. Please help

I have been using tretinoin 0.05% for 8 wks starting slow building to everyday use now. Still getting some whiteheads on forehead but my rest of the face is clear now. I want to continue tretinoin but have noticed that my face has got dull/dark than my body atleast by two shades. I have been using a chemical sunscreen with SPF30 everyday and usually stay indoors. I have no clue why my face is getting darker. Can I use glycolicacid+ acid cream or vitaminC in the morning to help evenout tone?