I have a male guinea pig around 5 and he is barely eating, he eats when we feed him from a syringe and doesn’t fight it. His coat is puffed and fluffier than usual. He has less energy and is making very few sounds. I’ve had two guinea pigs that have gotten sick before we took them to a vet and they got “Oxbow Critical care” but it was too late to save them and they passed away. But with him we gave it to him today as soon as we noticed he seemed sick. What else should I do?