Unexpected Death of One of my Boys

Question
I came home from work today to find that my beloved blue Dumbo, Ben, had died unexpectedly. He shared an extremely large cage (for ferrets) with another unaltered male (not a littermate, but introduced when they were approx. 3-4 months old). They were both on a diet of Harlan Tekland lab blocks and SueBee's mix as a supplement. Sam is (& Ben was) a year and a half old. After initially quarantining Sam when he first came home, and introducing the 2 rats into the same cage, Sam began sneezing about a month after for no apparent reason. Since then, I've taken each rat to the vet for respiratory concerns & was given Baytril. About 2 months ago, Ben was diagnosed with Pneumonia and given several injections and a full round of Baytril. It's become common to hear them sneezing periodically throughout the day, and I hadn't noticed any increase in the amount of sneezing going on. This morning, Ben was a little lethargic when I took him out of his cage briefly, but I figured that I just woke him up too early (they like to sleep in). When I found Ben, he was laying on his side, with no apparent tumors, open wounds, etc. The only thing I noticed was significant red crusting around his eyes and nose, but no other discharge. He also had a bluish tint to his feet and nose. Do you have any ideas as to what might have happened to Ben? I'm just devastated and concerned that Sam could have the same fate if I don't identify what happened to Ben. Aside from that, Sam is now alone in a gigantic cage without his lifelong companion. Sam is unaltered, and was always somewhat of the alpha rat, but also bonded with Ben once the initial bouts of fighting subsided. I'm concerned about introducing some new "friends" because of his prior respiratory problems, but I also don't want him to become lonely and depressed since I'm away at work for 10 hours a day. Do you have any suggestions? I'm just trying to make sense of the whole situation and figure out my next move. Thank you for any help you can give.

Answer
Your rat simply died of pnemonia,  we had one last year die the same way.  The red crusting round the eyes is just stress tears and is unconnected to the illness. I would get your rat a new buddy. Rescue a rat of around the smae age.

Were these petshop bought rats? Most rats from petshops have respitory illness. keeping them on woodshavings can also add to the illness. It is possible that your remaining rat has the same thing,  but there is nothing you can do.  Just go to a reputable breeder next time.