Guinea pig owners with Urinary tract infection experience?

I have owned several guinea pigs and currently own 2 boars. I have NEVER had trouble with urinary tract infection before, which I hear is very uncommon. Anyway, I recently purchased new fleece that is lighter in color than the old fleece bedding. I have noticed a few brown colored spots of what I believe is urine on their bedding. They have peed many places on the fleece, but only a few tiny drops spots here and there are actually brown. I was wondering if this is very early signs of a UTI? No squealing has been heard while urinating. I have palpated both guinea pigs and didn't seem to bother them. I am going to go get some cranberry juice today just in case, but any experiences would be helpful.