Need help with lite dog food

Maybe our dogs are like this since we raised them from puppies, but we always feed them some Iams, and throughout the day we give them carrots, bananas, sometimes some white rice, and just some misc vegetables/ fruits we happen to have that day. They are very fit and active. Our last chihuahua died at 18, but that was from some medications he was prescribed that the vet didn't tell us weren't supposed to be taken at the same time. But right up to that point he had a heart murmur and fluid in the lugs caused by the murmur, but even still he would run around all day like he was still a puppy, and every time when we came home he would jump repeatedly up about 4 feet up the door so he could see out of the windows of the front door, we'd see he little head bob up in the Window every second till we went inside. I'd say that if that medication hadn't have killed him he'd have easily lived past 20 with how fit and active he was at 18.