Everyone please know that I am far from an "expert" on this topic, so I am just speaking from an experience I had with one of my clown fish. I somehow purchased two of the most nervous and unsettled clownfish on the planet. They had been in my tank for about a month when I added a goby, can't recall exactly what kind he is, but he's striped, he is not the one that usually pairs with a pistol shrimp. Anyway, one of my clownfish became incredibly agitated that the goby was taking up residence near where he liked to hang out. He became very distressed and looked to have ich. As soon as I saw it, I put him in a quarantine tank, but he ended up passing away anyway. I totally freaked out thinking my tank was finished, but oddly enough the goby and the other clown fish did ok.
Sorry to hear about your sicky! I actually get pretty attached to my fish and I hate to lose one.