Hello,
I just got a Pom pup three weeks ago. Unfortunately, she ended up having a very extreme hypoglycemic episode (very close to death as per the vet). She did not have any diarrhea before this episode but on the way to the ER, she did have very loose bowels. We found out that she had Giardia. Our other Pom ended up getting diarrhea 3 days after she came home to us. We just contributed it to stress but found out Giardia is contagious and they were eating and drinking out of the same bowls. It is VERY common and can be taken care of with meds. Here is a link:
Parasitic Diarrhea (Giardiasis) in Dogs | petMD
Hope this helps.