Do output LEDs here need resistors?
As always, READ THE DATASHEET!

The chip you use has programmable constant current outputs, so you don't need external resistors to determine the current, the chip does this for you.

The current sunk by each output is ~ 10 x the current out of the Vref.



In your case 10 * ( 1.2 V / (1k2 + 680 ) Ohm ) ~= 6 mA, which is OK for a normal (20 mA max) LED.