Mine too! Reefs are great- knock on wood. Have 300gal reef and 93 cube reef both good. But 300gal fish only is a disaster. I’ve lost three fish. All fin rot. But had ammonia and nitrite spikes, and ick. And who knows what else. All the fish look sick. I test water daily and change water like every three days and sometimes emergent changes. Have 50gal fixed all the time now. Has been up since the weekend after thanksgiving. Was a tank transfer from 180 to 300.

Hope yours turns out. Did you read fourfordfamily’s thread on current diseases and quarantine. Maybe reach out to him he’s been super helpful to me. Hotrocks too. They are quarantining lots of fish now for huge system. May be able to help you also. Sorry for your troubles.
Where are you getting your fish from if I might ask? And what state are you in?
I’m in Wi and only get my fish fro
One LFS. Has been fine for years and now he is getting disease too. He uses copper in store and other meds to treat sick fish as they come to him. So sad all fish we have all lost. This use to be easier. And I thought fish only was easier but it’s not. What kinds of fish are you doing in your fish only tank?