I purchased two new female rats about a week ago. Both appeared (and still do) completely healthy--good coat, no sniffles, clear eyes, etc. I put them in a rack, separate tub, in my rat room. Since then, in the past week, I've had five of my adult rats, develop reddish discharge from the eyes, sniffles, labored breathing, hunched posture...and finally, they died. I have two separate rat racks, and rats in both racks have died. I now have another male who's looking sick, but everybody else appears healthy (including the two new girls). What happened?? I've never had trouble with my rats, and suddenly, I've got five dying in a week's time. How should I have introduced the new girls? Are they the cause of all this? I'm just really bummed and feel terrible that I might have introduced something that is killing my rats. Help?