Grand Cherokee headlights are some of the worst headlights out there when they get discolored, they look horrible and it makes it tough to see at night. You can't simply just clean it with some cheap cleaner, you must remove the top layer--bad layer of plastic and reveal a new layer of plastic. It takes some work but now my headlights look amazing again, try The Headlight Solution, their kit has everything you need to make your headlights look new again. Good Luck.
http://www.eastwoodco.com Type headlight refinishing kit in the search, get the autosol kit. Good luck, costs less than $20 good stuff.