Current-limiting for LED when Vf = Vdd
The nominal Vf for an led in a datasheet is given for a nominal If.  If your If is less than the If at the nominal Vf, then it won't conduct at that nominal forward voltage. Always look at the Vf vs If graph for your chosen led,  or test it with a constant current test circuit.

Also remember, that all those values are average, and your specific led may be above or below the average value. One led may be 3mA and another at 1mA for the same brightness, and at this low values, you may want to test and adjust resistors for each led.