Lost dead chromis
So I had 4 chromis, and one by one they have been dropping like flies. Each week, pretty much on the dot, one more goes. I'm now down to just 1. Now my parameters are perfect, ammonia 0, nitrite 0, nitrate 20. My temps fine, and the salinity is in the perfect range. So my first question is, why do they keep dying? I've read, and talked to multiple people and the answer seems to be, that's just what happens occasionally with chromis. Any other thoughts? There was no outward appearance of injury/illness, and nothing really signalled that they were about to go until they stopped swimming in the open water and hid for a day.
That brings me to my second point. I've got a 60 gallon w/live sand, and a wet/dry filter. When the second chromis died, I couldn't find him. I don't have a cleaning crew yet, so I was worried about a spike. (the aquariums been up and running, not including the cycling, for about 2 and a half months now). Luckily, as I was going through decorations one by one, I found him inside one of them dead. Now, it's like deja vu. The third one to die has mysteriously disapeared. I wanted to keep my eye on him when he went into seclusion because I had a feeling he was about to kick the bucket. I lost track of him, and now I can't find him anywhere. Does anyone have any reccomendations what to do, I'm 99% sure he's dead by now. Should I do anything to avoid an ammonia spike. I have two clowns in there right now that I've grown really attached to (George and Jerry) and I don't want a spike that'll kill them.