85C is fine. Your GPU will automatically throttle to ensure it doesn't damage itself.
If you can, get some extra case fans to make sure there's plenty of circulation in your casing.
It'll help keep your entire system cool and make sure your parts are keeping their maximum performance.
Ideally, you'd want a GPU with an aftermarket cooler to keep it...less toasty, but reference designs are usually that hot, so you don't have anything to worry about.