Has anyone found a method that will brighten or remove the discoloration on my older pillars and plates?

I've never had any luck using bleach. I have so many plates that have turned off white . 

I have tried (I think) any and all of the suggestions over the years and not one of thme really worked :(  I mention this in another post.  One of the suggestions I did not try was to put them in a mesh bag and soak them (overnight?) in a swimming pool.