About a couple of days ago i noticed my guinea pigs poop was mushy and really smelly. I contacted a vet in my area and he recommended that i give him about 2-3 drops of antibiotics directly in his mouth for three days and then after that 2-3 drops in his water for about 10 days. I gave him the antibiotics but on the second day I noticed he was eating less and on the third day as well. I was supposed to start putting the drops in his water today but he won't eat or drink almost at all. He's also not peeing or pooping. I don't think he's lost any weight but it has only been about two days since he stopped eating and drinking. I called the vet again and he said I should just let him drink and eat as much as he wants and not force feed him. I also noticed that he chews really slow and when I checked his teeth I saw that there was something black/grey/brown between his upper front teeth. There isn't any vets where I live that specialise in guinea pigs or know much about them. The vet said the most he can do is give him antibiotics and if there's something wrong with his teeth no one can help him. He's five years old and he's never been sick. I don't know what to do and I'm really scared. I don't want to lose him.