I know that carbon/BP are a factor, or seem to be, for many people. FWIW, we have never dosed carbon/run biopellets. We do have really good color and nearly 0 nuisance algae, so maybe we have similar conditions. (We feed really heavily.)
oh, I have also been using orca-labs nitraguard cubes. I can't remember if I said that. This tank has had some form of carbon dosing for most of its life. It was biopellets for ~2 years, but there was a major change to the way I was using them within a couple weeks of this starting for the first time last February, right before the whole tank fell apart and I nearly lost every coral. Then I didn't use them for 6ish months, and then started using the nitraguard cubes.
The only thing I can really do is try taking the cubes offline. I'm not sure how else to control nitrates however.