Feel your skincare. Take a moment. Check how it is responding and working not only with your skin type- but also your makeup routine.
Check also a different intervals throughout the month. Lifestyle, schedules, hormones, moods, food, the outer environment, medication and etc all play a role.
We are not static. We change from day to day. Being as observant as you can will help identify the right products for you and it will help in pinpointing the triggers.
Hope this helps!