I have two 8.5 yr old littermates. Neither have really been into food. The past couple weeks, our female has been extremely hungry and thirsty. She has never been like this. She steals her brother’s food, stands under my 8 mo old’s high chair when he eats (third kid, so this is not normal) and I just caught her in our pantry trying to get into treats. She’s acting fine and doesn’t seem in pain, but just really hungry and really thirsty. She seems like she is gaining weight too. Any thoughts?