I'm with the other moms who recommend having a discussion with the pediatrician about the longevity of the issue.
Instead of allergies (which is quite likely though I believe you'd see more of a whole systemic response vs. just diarrhea), my thought is more related to stress and how the move, the new environment, etc is affecting her.
My neice, around this age, was in a day care class she HATED. She had awful diaper rash that nothing could treat. The pediatrician put her on a restrictive diet (I believe she could eat chicken, broccoli, strawberries, rice milk, and a few other things). Nothing was being identified as the cause.
When she moved classes a few months later, the diaper rash went away. it was her body's way of dealing with stress when she couldn't communicate it appropriately.
Just a thought that perhaps, she's processing the stress of a move, a new environment, and unfamiliarity of her surroundings through physical manifestation.
Good luck.