Hiya,
I'm using Orijen puppy and James wellbeloved puppy food. As a treat I give some wet food like the Nature's diet pouch or the James Wellbeloved pouches. Occasionally I give Burns dry food, which you may find is easy on the stomach as it's not as meaty as the Orijen...all of these have samples that you can ask for to try.
I'm sure you are, but I thought I'd ask, are you introducing a small amount at a time? A big change will sometimes give Belle "zee runnies".
Good luck