Hi, I have to agree with Workndog as regards the high protein in the commercial dry food.
The ones you have been feeding are around 22%, much too high in our hot climate.
If you still want to feed dry and it is handy to have them familiar with eating a bit of dry food, look for something that is around 17-18%. They get enough protein from good fresh meat, fruit and vegetables without adding the extra imitation stuff.
I have found that for a tummy-troubled dog that the low protein Supercoat can be added and seems to help clear up the tummy.
I have on hand, in the fridge, acidopholis tablets for almost immediate relief for an upset stomach.
I hope your BC puppy is feeling much better and you have sorted through all the great ideas tossed your way.
Sue