How long has tank been running? I just went through a bad episode by it was what I believe was "new tank syndrome". Some reefers don't believe that exists, they think it's lack of attention to detail. It might be, but it's common enough to discuss.
Keep phosphates down. Rinse frozen foods. Don't over feed. Use binding agents. Keep up on routine maintenance. Update old bulbs. It will be self limiting.
I literally did NOTHING different and it went away, just as fast as it came on.