My skin tone has suddenly become dull lately.

I am posting this because I am concerned that my skin tone seems to have darkened overall lately. I don't have any specific breakouts, but I strongly feel that my skin looks less vibrant than before. I am not sure of the exact cause, whether it is due to lack of sleep or UV rays. I am debating whether to add brightening products to my routine, but I hesitate to switch easily for fear of irritating my skin. I am also wondering if I need to change my lifestyle habits first in this case, or if I need to rely on products. If you have found any methods effective for improving your skin tone, please share them!