Hopefully the Dunklin County Genealogical Society, 573-888-3561 can provide their death dates. Their deaths are too late to find on-line. The State of Missouri considers deaths after 1962 to be private and won't release copies of death certificates except to qualified requesters.
Maybe the Gen Soc will have their obits as well. If they don't, you can contact the State Historical Society of missouri, http://shs.umsystem.edu/newspaper/
. They will do a lookup and have the largest collection of newspapers on microfilm. Successful Searching!