Melafix and Pimafix are great for freshwater, but they're next to worthless in saltwater. This is old news, but it does illustrate the need to know what you are using before you use it. The rules of the game are different in saltwater when it comes to things like these which can alter the pH and redox in a big hurry.
The second problem is that you used such a med in the main tank, which also had inverts in it. Again, it really pays to know what is what before doing anything. Don't use meds in a tank with inverts in it unless you know there won't be a problem. Hospital tanks are for preventing this very sort of thing.
Okay, so now what? Obviously, the first thing to do is a large water change. Put some carbon to use, too. Some extra aeration couldn't hurt, either, especially since Pimafix tend to coat the surface with an oily layer which blocks gaseous exchange a bit. This isn't a problem in freshwater, usually, but saltwater holds much less dissolved oxygen in it than freshwater does.
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