What emerald said, you will know more when you get water tested.
I expect your phosphates to be high. I also anticipate that your food has fine particles creating a cloud in the water that fish can't eat and is in in excess of what your corals consume.
I say this because I have been there too. What helped me was to grab an auto feeder set to low, so I couldn't over feed and got a more intense red spectrum refugium light.
I later dumped the refuge and currently have an ats which was an improvement. Also dose alk, cal, and mag through a cheap jebao which has worked great. Current tank under construction will have gfo, carbon, two marinepure blocks, dosing carbon, and grossly over sized skimmer. I have grown tired of algae harvesting. I would rather pour out skimmate than throw away algae.
Sent from my SM-N910V using Tapatalk