Any fixes r tarnished costume jewelry?

Use a silver cleaner for a Tarn-x product.

I would use something specifically for jewelry, such as, jewelry cleaner, you can get it anywhere. There is also non chemical cleaning techniques, check this site out for those: http://www.jewelrynotes.com/how-to-care-for-stainless-steel-jewelry/

You could try rubbing with ketchup but costume jewelry-the 'silver' finish has probably worn off-

Is it silver or silver plated? Tarnex likely too strong for plate. For a few dollars you can get a jar of silver-only cleaner. Dunk, rather than soak, if it’s not marked sterling (usually on the clasp). Rub with old tshirt or cotton sock. Then again you can just try good old toothpaste and a very gentle old toothbrush to get between links.

try plain white toothpaste

Don't use tarn-x on silver plate, it will eat it away! Try plain original toothpaste with no gel or anything added, and a toothbrush. There is also a possibility that the plating may be wearing off. It is only a thin coating of silver over another metal, so you have to be careful to use things to clean the plating that won't eat it off.

You can use a mixture of warm water, salt and few drops of Dawn dish soup. Place tin foil in bottom of pan, soak few min. Rinse and wipe clean

Try equal parts baking soda and apple cider vinegar, gently working it in with a soft toothbrush.

I found on pintrest.com that a glass of sprite will clean the tarnish off. It worked well in the video. It was one of those "hakes".