Building DIY TrackIR, need wiring help
When each LED has its own resistor you only consider one LED when calculating it. 

Effectively you have three independent circuits.

The presence of the others will cause the battery to sag a little, but the operating voltage will vary through their life anyway.

Note that LEDs to be detected should be modulated, this seems to be a fairly crude approach using power instead of sophistication to make them distinct.