congested breathing

Hi everyone, I would really value your thoughts and suggestions on this: I am having problems with 2 of my guineas (they do not cohabit but are in the same room near to each other) and that ruttling they can do. One has had it a while (a male) and another (female) started to do it a couple days...

One of my guinea pigs has always sounded congested, although my other three guinea pigs sound perfectly fine. Some days, though, like today, she sounds way worse. She still eats and drinks fine, and her poos look healthy. She's always been a little lazy, but she isn't any more lazy then she was...