Is it okay to use tretinoin, vitamin C and glycolic acid?

You can certainly use these two skincare products together as this is a great anti-aging regimen.   Vitamin C should be applied in the morning before your moisturizer and sunscreen.  You can apply Retin-A at night after washing your face.   Retin-A can be irritating for certain patients, so I usually tell patients to use a pea-size amount for the face and start applying every other day until daily use is tolerated.  Follow-up with your prescribing physician for his or her recommendations on this!   Thank you