[PhilOlsen]

Loose the undergaravle filter, it is most likely the cause of your issue, even if unudes you will have lots of build up unders the plates that you cant get to in order to clean. I would do this:
1) remove all the crushed coral and undergravel plates

2) put down a sand bed, placing you rocks on pvc not on the sand

3) do a lot of water changes, at least 50% weekly until things get under control

4) put any livestock into a QT tank until the process is done.

5) turn your sump into a refugium