Dear Mr. Benton,
Thank you for posting your request on History Hub!
We suggest that you contact the Georgia Department of Public Health to request a search for the death certificates of John Robinson and Ada Robinson. For marriage records, you will need to retrieve your documents from the Grady County Probate Court if that is the county in which the marriage occurred.
In addition, the FamilySearch Research wiki for Georgia Vital Records may be helpful.
We hope this is helpful. Best of luck with your research!