My boy has been on Fromm LBP since day one. He won't eat anything else so he's currently three and still eating the puppy food. We never had stool problems on it. I'm not sure if less fiber is really the answer...when my boy gets a little soft we usually add pumpkin to his food, which is a lot of fiber and it fixes him right up.
But I think it wouldn't hurt to try to switch. It's a great food, made about 20 minutes north of where I live.
CD RE TC HIC 7/10