dc42:
My guess is that you had a wiring fault that you haven't found yet. The other possibility is that both of those LEDs require a higher than normal forward voltage, but that is unlikely.
If I understand him, could have just been one bad one, but he kept it with the other as a set. Outside that, maybe one of the resistors is wrong by a factor of 10 or 100. With him putting the LEDs in parallel, I would have expected the OP to be mentioning that the brightness was off on those; he didn't.