Puppy Diarrhea

Question
Our puppy has had diarrha during the night for the past 3 weeks or so.  She is 18 weeks old.  The Vet put her on Flagel for about a week and that seemed to fix the problem, but the day after her prescription ended, the diarrhea began again.  We have been giving her some Pepto Bismol (again vet recommended as a possible solution) and that seems to help but we can't that to her forever.  He has taken stool samples and can't really find anything and we have been left scratcing our heads.  The vets most recent thought is her diet, we had been using Science Diet puppy and he switched us to I/D.  Our pup maintains her vigor and wrestles with our other golden, all incidicators would say she is fine, eating and drinking well, but then diarrhea at night.  2 days before the day began we got her second set of vaccines, could this be it possible?  The night before she was around my fathers "little" dogs, could they have gotten her sick?  We don't know what to do, any ideas???

Answer
I wish I could be more help, but I don't have any medical background.

What time are you feeding her last meal?  Maybe move it up a little so that she has time to poop and empty her bowels before going to bed for the night.

Is her stool normal at other times during the day?

You can try adding some canned pumpkin to her food.  This would be the product without anything added, just pure pumpkin, NOT PIE FILLING.  Ask the grocer if you have trouble finding it.  Sometimes the fiber in it helps bulk up the stools.

If all else fails, there's no reason not to ask a second opinion from another vet.  That's the same as what we would do for ourselves if needed.