thanks so much for all the replies...here is a png of what i had wired up:
it's controlled by a tip120 with a diode and a 1k resistor going to the arduino pwm pin.
now what i have is the last two LEDs aren't in series...they're in parallel...with one 120ohm resistor for both, 1/2 watt, which is definitely overkill but i don't want to burn them out again. they are just slightly dimmer than the others that are in series. It's been working fine for a few hours but i do need this to work for around 7 hours a day for a month. you think it'll be okay?
thanks so much for the help