In medieval times there was no concept of germ theory, nor was clean water readily available, as the great Thames was used for drinking, washing and flushing of sewage. There were no vaccines, antibiotics or surgery (unless you were really desparate and had it done without anesthesia). People died from influenza, plague, smallpox and tooth infections all the time. King John (the Magna Carta king) died from dysentary, a gastrointestinal illness that is treated today with antibiotics and intravenous fluids and is rarely fatal. . Most monarchs were married off as early as possible (in women, sometimes as soon as they had there first menses) so that they would have heirs to secure the royale succession. Women died in childbirth in large numbers, or soon after from puerpural fever. Men usually died from infected wounds, or typhus, or influenza. . I would check in wikipedia under the individual monarch's names to see if a cause of death is supplied. And in medieval terms, '50' was a ripe old age, and in keeping with the bible, you got your two score and ten right there.