Consider the following verse regarding prohibited vrat
Gandhari fasted on a day when the tenth and eleventh phases of the moon were mixed. Her hundred sons perished. Hence such days shall be avoided for fasting purposes.
Tenth phase of the moon is Dasami and eleventh phase is Ekadasi. Fasting on the day with both Dasami and Ekadasi is prohibited according to this verse.
Do any other scripture mention this as a reason for perishing of Kauravas?