Tom, What are your PO4 and NO3 readings and do you track them just after and before water changes? One answer is obviously to limit the food (nutrients) going into the tank, but with all those tangs, that might not be possible.

If you accept Feldman's skimmer performance study, the best skimmer will remove less that ~30% of DOCs. In addition to your Bio Pellets, Carbon, Phosphate removal media (GFO, Phosban, Po4X04...) Organic scavengers (i.e. Purigen) are additional methods to remove DOCs.

A few thoughts...
  • Filter socks - Are you using them? If not - add them and change them frequently to try and intercept and remove detritus before it breaks down into nutrients.
  • Depending on your Phosphate and Nitrate numbers, I probably would add a GFO and GAC reactor. To limit concerns of LLD, use a good quality GAC such as ROX 0.8 which requires very little rinsing and produces very few fines.

And lastly, remember the Reefers Creed - "Only bad things happen fast" As you know it will take time to lower nutrient levels and see the positive results, especially is higher phosphate levels have been present for a while as you may have to deal with PO4 leaching from your live rock extending treatment length.