I am concerned about one of my rabbits. He is a Rex mix born in June last year. This morning when I fed everybody he stayed hunched in the corner. He is usually my friendliest rabbit. Always hanging out of the cage for treats and pets. I offered him his favorite treat, a cheerio, and he did get up and take it. But he spat it back out and opened his mouth quite wide a couple times. The he went back to same corner and potion. His butt is clean. What do you think? Oh and hi ears are cold compared to my others.