byteofthat:
Any more ideas now that the effect seems to be spreading?
It will spread if something is wrong. Can you make sure you have a 220 R resistor and that the voltage is 5V.
You need to subtract the forward voltage of the LED. Being white it might be as much as 3V so with that resistor you would get (5-3)/220 = 9mA. That should be well withing the limits of an LED, unless they are faulty or as I said the resistor or voltage is wrong, measure both with your meter.