Question about toothpaste and/or oral hygiene products

Hi everyone,

For a bit of a background, when I was in my home country, my oral hygiene routine was very simple: brush my teeth twice a day in addition to using gum sometimes here and there. Barely visit the dentist for any kind of teeth whitening procedures and my teeth were completely fine, as white as snow. Toothpaste wise back then, I didn't use any expensive or special treatment ones either, just average popular ones selling at supermarkets. I don't smoke or vape either.

But lo and behold, after a while living in Japan, my teeth has started turning yellow with the exact same oral hygiene routine. I even copied my Japanese co workers and started brushing my teeth 3 times a day (an addition one after lunch). I don't know how it went wrong, but since the oral hygiene routine is the same, I am assuming that the issue is with the toothpaste. I am using the extra whitening type but doesn't seem to improve at all.

My fellows, are you experiencing the same problem? If you do, what did you do to keep your teeth shine and white? Do you have any recommendation on toothpaste or extra oral hygiene products?

Edit: Have been living in Japan around 4 years and vocab mistake

Edit 2: Thank you everyone for your advice! The reason might be because that I have started consuming coffee excessively in this one recent year.

by TrainingInvestment78