Ketchup will do the trick!
Brasso removes some of the brass coating. Use ketchup. Slather it on or soak in ketchup for a while. Wipe and rinse.
You can use good ole vinegar and baking soda! Pour the vinegar on first and then sprinkle the baking soda. It may take a couple times of repeating depending on how tarnished they are, you may even want to soak them in vinegar and then sprinkle with baking soda! Hope this helps!