Man. It's always a bummer when you lose fish. Sorry to hear about that.
I run my drip system through my sump. The drip line of fresh, decloraminated water enters at the top of the tank. Excess water leaves through a bulkhead in my sump thru a line I ran under the house, then out to the garden.
I only run fx5s on my large tanks. I have 4 going in total, with a backup fx5 and spare motor in case anything breaks. Each one is set up the same: pond matrix in the 3 center baskets with sponges on the sides. They keep the water clear and does great with the bio load.
I think your matrix reactors' flow might not be high enough to maximize the bb growth.
For record, I think eheim is good too (I have one installed on the tank in my avatar)
Until you get the water quality under control, you should do partial water changes every day.
^ agreed 100%. Great feedback