With something like that happening so quickly I would check your water pump first.
My bad experience with the AG original is that the roots get too bulky and end up clogging the sytem. At least this is what happened to mine; the roots worked their way right into the pump and killed it by the time the plant was 9 inches tall. By the time I realized the pump was out it was too late. But I did manage to get ahold of a new free pump through their warrenty, and a batch of veggie seeds.
I still use my AG; As a clone machine. I take cuttting and put them in rockwool in the AG and turn it on (with proper H20). After a few weeks...... roots. Its perfect for this.