Could you please give us a better description of how your system works? a "true" aeroponic system mists the roots something like every minute or two. what some of us call aeroponics and is affectionately referred to as 'soakaponics' more or less splashes the roots and is done something in the range of every hour or two.
If all you're watering it is 30 minutes 2x a day, the leaves are probably dying from dehydration.

what does your system look like? Ive been wanting to try my hand at hydroponic trees for some time but I don't have the patience.

As for the leaves turning color and falling off, thats a pretty typical response to transplanting from soil to hydro, it takes time to acclimate. Keep an eye on her, if the defoliation continues, check to see that the roots arnt rotting out. if they are, cut the roots back a bit and wash with h2o2 to kill off some of the bacteria.