Silver Tarnishing/Why is it Turning Black ?

Why did my silver jewelry turned yellow, then after a rainbow color hue and finally black ? It can happen in a matter of just a minute or two.Must of been right after being expose to water ? The water could of have chloride, causing a chemical reaction against the .925 sterling silver.

Our .999 silver pieces can get cleaned with just Dawn soap, hot water and a brush. As for the sterling silver, there's many tarnish removing solutions in stored that help that problem.