Wet Chin?

Question
Hello,
I have read over some of the questions and I can't seem to find an answer that fits my guinea pig.  I have a male, Lupe, about 4 years old, I think.  I give him plenty of greens, lettuce and such, as well as carrots, apples and pears. He gets Timothy Hay every night and has always been very active, and vocal. A couple of days ago I noticed that he wasn't he usual chipper self in the morning, usually when he hears me chopping his carrots he will start "talking" to me, he has been very quiet, and he isn't so active. Then yesterday I noticed that his chin is very wet.  He is still eating, though not much and he does still come out and let me pat him but he isn't as active.  I am not sure how else to describe it.
I have never owned a piggy before, and there is nothing in the book I have about a wet chin, or him not acting like himself really.

I appreciate all the help you can give me,
thank you

Answer
i think the wet chin is happenstance of something more serious, a decrease in appetite and less social interaction as well as decreased movement usually suggests something serious too.

check stools, see if they look like they usually do and if there are as many as usual, I would also recommend getting him to a vet.

also have the vet check at his teeth, make sure that they are not too long, or mishapen, it could explain all of his symptoms, though really that is just a guess, it could be something more serious.