Upon beaming down to the planet surface in the first shot, the buildings are round, with alternating light blue-green and white panels. After a few shots and Kirk, Spock, and McCoy discussing Kirk's previous conversation with Dr. Robert Johnson, the camera is trained on the "ribbed" building again, except now the alternating panels are light plum or purple and white.
After Johnson dies Dr. McCoy says, "Last one, Robert Johnson. Cause of death: old age." Medically speaking, old age is not considered an underlying cause of death; it's not even considered a disease. The morbid condition that resulted in or caused death is this case would most likely be cardiovascular disease.
Dr. McCoy states that the landing party is aging at the rate of 30 years per day. Spock then states that the landing party only had, at most, 7 days to live. At the rate that Dr. McCoy mentioned, the landing party would be in excess of 210 years old physically when they died.What if Spock just calculated for how long he had and applied it to the rest of the landing party?