From Macadamia to Yellow!

We have had a few issues with our product, firstly it Cracked and fortunately the installer was Quick to replace to piece of Quartz that broke but then we realized how Yellow the Product has become, compaired to the new peace it is visible obvious that the Resin used to make the product has become aged and Horribly Yellow! What is suggested, they sent someone out to come have a look and they have just said tough there is nothing they can do, this top has a 15 year warranty and we are far within this time frame.... The Installers have tried to help put the supplier is not offering any assistance, just get someone to clean it and the guy quoted about R25 000 to do this! I just do not feel the same about my kitchen anymore...