Commercial disks, which Apple uses, are pressed and cannot degrade like that. If this was a brand new Mac, then either someone switched out the disks, or they were stained in some other manner. If you bought it used, then it's likely you were given copies. If they are original disks, they should be gray with white silk screened lettering. Anything else is a copy.
If you want machine specific replacements, which would include the bundled iLife software and other titles that are not on the retail disks, contact Apple. They will ask for the Mac's serial number to make sure you get the correct disks.