mouse making noise

Question
One of my mice is making a really strange sound. She makes it, it seems, when she is sniffing, which worries me that it is a upper respiratory issue. It almost sounds like a garbled squeaking. I only use care fresh bedding, which is like a soft recycled cardboard blend, so its not very dusty. She is kept with 2 other females, and the cage is changed weekly to prevent any sort of ammonia build up. The other two mice seem to be fine, one of them has hair loss, which I determined was mites and I'm currently treating for. All her other behavior is normal, she's eating, running on the wheel and loves to run around in her mouse ball. Any ideas of what this could be? I've had her for over a year, and this just showed up in the last week or so.  

Answer
Dear Emily,

You're right that it could be a respiratory infection. Can you take her to the vet?

If not, you can treat her at home; however, the vet has better remedies than you can find over the counter.

The following post explains how to use Tetracycline, which is available in a pet store.

http://en.allexperts.com/q/Mice-3824/2010/6/respiratory-infection-mouse-colony.h...

I wish her the best of luck and health.

squeaks,

Natasha