My Moe is dead

[Coleus]

Well. my most favorite fish has died :-( He was my first fish and fat and ... healthy, guess not. He is lawnmower blenny


On Tuesday i saw him breath rapidly and stayed in the small cave, then swam out and kind of bang his head into the rock and then disappear behind the rock. I thought that was unusual but not sure if i was right so I watched all other 22+ fishes and I saw no sign of parasites or distress, tested my water everything is normal. Yesterday, did not see him so kind of concern, today i heavily feed the whole tank in hope he will smell his favorite food and come out. well still no luck, so i track down where my blue hermit crab is heading. After awhile, my hermit crab finally land on his body in the back of the tank. The head and tail are gone. All others fishes are normal. no parasite found on any fish.

I don't get it, my last fish i added to the tank was 3 weeks ago and it was a trigger. I normally saw him chasing my bicolor blenny but nothing serious. Who can kill him?

Kind of sad because he is my first salt water fish and he is very cool. I don't get it, can anyone tell me why? I don't think he is die because of age because he is only 6 inch long.

So sad, now i have to find a replacement