normally tretrinoin is used for a night time only due to stability of drugs. if you use both day and night time, i suggest you to stop using at day time and use for a night time only, apply moisturiser ( i use physiogel A.I. Lotion) the amount of tretrioin matters as well, using only pea size only!!!!
if you have acne, try Skinoren, it's 20% azelic acid which works for acne and can be used for day and night. and can be used with tretrionin at night time too.
try to add niacinamide with tretrinoin, it helps for irritation.
and sunscreen day time.