Those 3.27 voltages are perfect.
Are you saying that the Adafruit library shortcuts the SDA to GND ? Perhaps pin 31 or 32 on the Due is shortcut to SDA pin 20 
Can you select other pins to select the sensors ? Change all the 30,31,32 to other pins.
There are a few more options, it does not have to be a shortcut. Sometimes a sensor gets confused and keeps the SDA low. Do you have a Logic Analyzer ?