Yellow stains after cleaning silver
I suggest to do the following: 
Line the bottom of a pan with aluminum foil. Put the silver piece on top of the aluminum foil. The silver piece and aluminum foil must be in contact with each other.
To about 2L of hot boiling water add about a half cup of baking soda (Be careful!). Then add the mixture to the pan. Make sure to cover the whole silver piece. The tarnish will disappear within several minutes.
The chemistry underlying this treatment is the following:
The silver tarnish is the chemical product of the reaction of silver with sulfur-containing substances in the air, $\ce{Ag2S}$. Silver sulfide is black. In this process, we convert silver sulfide to silver according to the following reaction:
$$\ce{3Ag2S + 2Al-&gt;Al2S3 +6Ag}$$ In fact, aluminum has a greater affinity to sulfur than silver.  The reaction between silver sulfide and aluminum takes place when the two are in contact while they are immersed in a baking soda solution. And it becomes faster when the solution is hot.The silver piece should touch the aluminum because a small electric current flows between them during the reaction. The formed aluminum sulfide may adhere to the aluminum foil, or it may form tiny, pale yellow flakes in the solution. 

The advantage of this method of cleansing is that we do not remove the tarnish with some silver. We simply transfer silver sulfide to silver.