Layering question(s)

I have started tretonoin. I use it twice a week so far. The day after I use it my skin is a little sensitive. Regarding serums, what can be used before the tretinoin? I just got the Cosrx The 6 Peptide serum, and I also have Dr Re-Ju All copper peptide. Not exactly sure when to use which! I figured one in morning and one in evening? Please help! 🙏