Not school related,i need help on finding a dog food.i have 2 chihuahuas and ones getting older,she's having problems with her back and joints it seems.weve been feeding them Rachel ray and they did fine&we've always fed them Purina,no problems.i would like one that isn't too expensive.they don't really eat a lot they're only.5&8 pounds appx.can anyone help?ive noticed that recently they don't like the purina dog food & we feed them the soft kind to help with digestive .