Powering up several teensy boards
Given your clarification that the Master is a Teensy 3.2 and the Slaves are Teensy-LC you should NOT connect the 3.3V output of the master to the slaves. 

Referring to the two schematics you will see that in the Teensy-LC the 74LV1T125 is powered from the Vin (+5V) so this devices would be un-powered if you only connect 3.3V rails. 

The best option would appear to be to connect the Vin from the Master to the Vin of the Slaves and the GND pin from the Master to the Slaves (don't use AGND as it's connected through Ferrites to GND). 





NOTE: The Teensy-LC processor has an built in 3.3V regulator, so powering the Vin pin with +5V is the best solution.