Is it normal to have teeth whiter than others?

My front teeth are pristine white. The side one on each of my mouth are off white and it’s annoying me. I know they can’t all be perfect but is it worth getting them professionally whitened if I’m unhappy or will extra brushing these specific teeth help?

Get them professionally cleaned. No amount of brushing will clean it up and make it white.
On that note, toothpaste is kinda a fad. The important thing in brushing your teeth is the brushing itself, to remove all the yucky things on your teeth. Toothpaste is there just to make things pleasant (and give fluoride, but any brand will do the same).