I have two Guinea pigs, both males and three years old. Alvin occasionally makes this wheezing noise, usually late at night when everyone is trying to sleep. Sometimes he stops when I put food in his dish. For the past few days, he hasn't been very active and he won't come out of his hiding hut to eat. I have to put his food just outside the hut door, he'll poke his head out just long enough to eat, then goes back inot hiding. I'm not sure what to do. I've had them for two years and they've been fine so far. Oliver isn't active either, and not eating as much. I clean their cage twice a week, they get fresh water everyday, they aren't near any windows or doors. I'm not sure what to do.