My situation is similiar to a man's FAQ under diatoms. Next is ensuring your water is phosphate free, test it, and switch to purified if your not already using RO or similarly processed supply. Our 90G reef is about 18mths old and is generally very happy. It's mostly soft coral with 120lbs of live rock. We run about 1200 gph circulation, generally lighter flow but covering most all corners.
All water chemistry is pretty much on the mark.
Additives are iodine, MW Black Powder and phytoplankton. Also, calcium, strontium, buffers etc only as needed. All lighting is well under its age for change out. When the halides are on, we get a ton of tiny bubbles on the gravel and some rocks. Leaving the halides off stops this little cycle, however the corals are much much happier with the halides.