Marina and the Diamonds have been forced to cancel their upcoming UK tour dates after the band's frontwoman, Marina Diamond, developed a condition in her vocal chords, according to an announcement on her official website Monday.  "Today the doctor has told me that I cannot sing performance-length shows while I undergo treatment, or I could cause permanent damage to my vocal chords," the singer added.  Diamond did not say when, or if the dates would be rescheduled.