[matese]

I don't like the darker color patch in the stool, that could be blood. Other options are it could be stress in the move, could be anxiety because of your mom not being with him, it could also be the change in the water. This may sound strange but it's a fact. Years back I moved from the city to the country, we had well water in the country, my dog had loose stools. I still worked in the city so I would fill one gallon bottles of city water to take home.
Another water story
I rescued a 2 1/2 yo little boy 3 years ago, I am in the country, well water, this boy came from the city, he was relayed to Pa. he had loose stools when he drank tap well water, I put him on bottled water and his stools are perfect.

I would keep my eye open to see if that dark patch remains in his stool. Sometimes if you feed a dog something he is not use to eating, when he passes it in his stool it is a bit darker then the rest of the stool.