Blue Throat Trigger strange behavior

Our Blue Throat Trigger has been in our tank for almost three years. Great little fish, very friendly and fun to watch. ALWAYS is out to eat, and when the lights come on in the morning. Yesterday, he didn't come out at all. He stayed wedged in his sleeping spot, but was breathing, and moving his fins occasionally. Last night, before the lights went out, he had turned around (I've never seen him in his spot backwards.) This morning....almost the same spot, but still breathing, and occasional fin movement.

What could be causing this? The ONLY thing added to the tank recently was new matted filefish to replace the one we lost a few weeks ago. The new guy didn't make it too long, was isolated in a breeder box, and died. All other fish are acting perfectly normal. It is very odd behavior for this trigger.

Any advice would be appreciated.