Nope. I have a 105 which is 4' x 24" x 21"....just a little deeper front to back from your tank, and i have a 2400 gph power head in it along with a 1500 gph return pump and I think it's not enough flow.
Putting something new, like a powerhead, into the tank might have stressed it a little, but not enough to kill it. If you just did a water change, is there any chance that had something to do with it?
Sorry for all the questions, but...How long have you had this fish? Are there other fish in this tank and how are they doing? What were your parameters prior to the water change and what were they afterwards? Do you do frequent water changes?