One full can? If it's the large cans then that's way to much. What brand of canned?
It could be the Iams that has given her the runs..Especially if you switched her right over without making a slow change. Some pups/dogs can't handle a quick switch over. When switching to a new food, you need to mix it in with the old then slowly take out more of the old and add more of the new.
My nephew has a 15 week old GSD puppy..Before they got her at 9 weeks they called me and asked what she should be fed...I suggested Chicken Soup For the Puppies Soul dry and canned..She is doing great on it. They did the slow switch over.
"A dog can express more with his tail in minutes than his owner can express with his tongue in hours."