i'm not familiar with the board in question, but often, the LED's are wired between a 5V power "rail" and ground, each with a resistor in series with the LED for the purpose of current limiting.
If this is the case with your board, you should be able to use the calculator for a 5V source, and use that value resistor for them all.
Of course, I'd wait for another person with 38GT experience to chime in before committing to a value, but at least now they can quote this post and agree or disagree.
I could tell you for sure if I had a layout diagram, or even good pictures of both sides.