Sorry you had to find out the hard way that presentation cases are not intended to store your handgun (they are for "presentation" or display purposes only). The flocking materials can degrade and in many cases cause irreparable damage to the finish on a gun. This is why, initially, the factory wrapped the gun in protective paper before shipping it inside the presentation case and, later, shipped the gun in its own cardboard box, separately from the presentation case.
22hipower's recommendation for returning your stocks to original condition is a good way to proceed. However, sometimes an entire stripping of the original finish is necessary. A soak in acetone to remove the original finish and then a light spray of a finish lacquer will restore them to original condition. Sometimes some light sanding is necessary prior to the refinish.
There are some gifted grip refinishers on this forum if you are reluctant to undertake the task yourself. Good luck to you whichever way you decide to proceed.