I can't really give any advice on the Iams food that you have her on but my little guy was on Eukanuba puppy and we decided to try Purina Pro Plan toy breed puppy and he is almost completely switched over to the Pro Plan now and he likes it. It hasn't been hard on his stomach and his poops(maybe TMI) are still firm and normal looking. He is a healthy active little pup!
The food works for my puppy but i know that every dog is different and some people would oppose this food so i'd read what others have to say as well.
Good luck finding a food that works for you and your baby!