LED's don't really have "resistance". They have a quite non-linear voltage vs current characteristic.
To run them in parallel, you need a separate means of current regulation ( a constant current source, or a resistor )
for each one.
You can also connect them in series if you have a high enough voltage source, and then you only need one
means of current control.
Yeah, I sorta understand that they are non-linear. But if you know the Vin and the voltage that each diode will stabilize at, what happens if you use only one resistor? Can you not calc the current flow? Or is this not a good idea as the stabilized voltage will drift over the life of the LED causing the current to shift as well?