Poop problems

Q: We have a 4-month old Cavachon puppy who has developed a case of diarrhea. Over the past several days, she will hardly poo at all during the day, but will go at night, then wake us up two or three times in the middle of the night to go to the bathroom. It seemed to resolve on its own a few days ago, but it started up again last night. Many times when we take her outside in the middle of the night, it's just a small amount of poo, about the size of a quarter. It comes out pretty quickly, then she spends another minute in the pooping position even though nothing is coming out. There has been no changes to her diet of Royal Canin dog food. She's not yet allowed free roam of the house, so she's not eating any other food substantially. When we take her outside, she often likes to chew on mulch, which we discourage. The bouts started right after she got her rabies and flu shots, but we think that may just be coincidence. What are some reasons that we could be seeing these bouts of diarrhea? And what is the best way to treat it?

A: I think it best if we could speak about this situation as there are many variables, is there a convenient time and number to reach you so I can help?