What disease is this?

[GGhana]

So I'm dumb and haven't been using a quarantine tank. About 5 days ago I added an orchid dottyback and a few days later it died seemingly stuck in a rock it couldnt get out of, no symptoms beside a torn up fin. The next day a chromi died in the same way. Yesterday my lichen starfish started having limbs fall off, my royal Gramma died which looked pale and white and now today I lost a clownfish that also looked like a white powder was on it which may have just been sand dust. This is leading me to believe it's marine ich or velvet. However, one of my fire fish is currently twitching like a seizure and the last reef chromi has a red sore like Uroema marinum which it's had since I got it (didn't know this was a sign of disease and thought it had just got in a fight). However, this is one of the few fish still alive. I also have a white clownfish that is covered in white tendrils and isn't looking to hot. All of this happened in the past 2 days.

I've basically resigned myself to losing all my fish at this point but what do I need to do in terms of cleaning up my tank? I still have snails, a cleaner shrimp, hermit crabs, coral, and a pink pincushion urchin. Will those be fine?

Thanks

 

[maleks.reef]

Posting pics will help others help you. IMO it sounds like ick but i could be wrong.

 

[Sharkbait19]

Would likely be brook or velvet for the timetable, probably velvet as that is more likely to be taken in by a dotty.
Quarantine and treating with copper is a must to prevent/kill this.
The twitching sounds like flashing, which is its way of trying to itch itself. They are quite disease hardy, so it might not be too late for the firefish.
As for the tank, it should remain fallow for at least 6 weeks, which means nothing new gets added in that timeframe to starve out the disease. I’d recommend picking up any corals or inverts you had your eye on beforehand, as you won’t be able to during fallow (and after it would be wise to at least dip corals to reduce chances of disease transfer). Inverts cannot get sick from fish diseases, but can carry it, as the eggs (tomonts) sit on surfaces.
The star dying sounds like it would have been due to a param swing after the deaths, or like it’s starving. They starve in too small of tanks, and the limbs begin to fall off.