Should i layer on my glycolic acid face moisturizer or should i just use it for night time? can you layer vitamin c serum whith a retinol serum?tyvm

I don't think: it matters if you use the glycolic acid in the morning or night application, but most would advise you use your retinol/Retin-A the opposite time of day. Many find the glycolic acid too drying/peeling for use during day (peeling looking skin). I recommend avoiding vitamin C serum at the same time as retinol; consider using the vitamin C every 2-3 days in place of glycolic acid. Good wishes:)