I know this isn't exactly what you asked for, but it still might help you:
To assimilate nitrate (NO₃) corals, algae, and bacteria reduce it back to ammonia (NH₃) first. This requires enzymes (namely
nitrate reductase and
nitrite reductase) which are based on trace elements (It should be molybdenum (Mo), and iron (Fe) or copper (Cu) depending on enzyme and algae/bacteria/...).
Have you tried providing these trace elements in small amounts regularly/daily to help ensure these trace elements are not a limiting factor?
Another possibility would be a phosphate (PO₄) limitation which would stall carbon and nitrogen uptake. Carbon, nitrogen, and phosphorus are taken up in certain ratios to each other and if one of those elements is missing, it limits the uptake. That's why carbon dosing is often useful as it fixes a carbon limitation which appears to be common in reef tanks.