Well, there is still cause for concern in my opinion and had it been my tank, I would still check ammonia, nitrItes and nitrAtes as that can help you see if there was something preventable you could do in the future to prevent fish from dying. I am truly sorry for your loss. When you say clean out the whole tank, what exaactly do you mean? If it is a long-established tank, I would certainly do a major water change. I need to know more about the tank before i reccomend that though. How old is it? How big? Do you have other occupants in the tank right now?