I am also sorry to hear of your loss. I know how hard it is to loose one.
For those who were asking what a URI is, it's an upper respiratory infection. There are lots of reasons they can develop this, either bacterial or fungal or possibly viral. Can occur from poor ventilation, high environmental load of bacteria or fungi, temps to hot or too cold, vitamin defciencies, infectious disease, and other. Also, if a cham has any other problems (other systemic infection, organ dysfunction, or other) and as chams age their immune system may not be functioning as well as it used to and may leave them more susceptable to infection that they may have previously not been susceptable to.