All LEDs died yet rest of board fine; why?
I'm proposing a scenario (or two)...

The typical forward voltage of these LEDs is 2V so, a 70 ohm resistor is going to limit LED current to 1.3/70 = 18.6 mA (perfectly fine). If however, you managed to get 5V on the rails (by mistake) then the peak current could be 43 mA and exceed the continuous rating for the LED (30 mA).

Also, if you operated at a temperature above 50 degC then the maximum continuous current does fall - anything that might cause the LEDs to become overly hot?