At this point you should change the water and redose to 1.5 mg/l ammonia. When the amount of nitrite goes off the chart you have no way of seeing how well the filters are consuming it. And high nitrite can interfere with the growth of the bacteria.
Rather than change out the water in the containers, I would just move the filters over to the tank, dose 2 ppm ammonia and see how it looks 24 hours later. You have a complete cycle already, you just don't know the strength of the bacteria. It might have the capacity for only 2 fish - what you want is for it to process 2 ppm with no nitrite after 24 hours. That would be a strong enough biofilter to handle a whole group of 6 discus on the first day.