There may have been a recent, specific "food incident" then.

a few sprays of crumbs from taking a bite of sandwich, cookies or crackers, closer than usual...

as an experiment you can try just gently blowing (purse lips tight to do this) under JUST ONE of the problem keys to see what happens. if it is a crumb, the problem might go away... or show up on an adjacent key instead, either way you get a clue.

don't blow on your whole keyboard though. compressed air is best because it does not contain moisture like our breath. Also that nice skinny straw lets you really take aim.

~ waves ~