Sometimes it takes some babies a bit longer to get their digestive system used to a different food. Introducing the new food over a 3-4 week period is a good idea. Sometimes some will need longer.
When I switched mine to LIfe's Abundance back in June it took me about 3 week. Since then they have had less turds as there are no additives in the food. I'm very happy with it.
Lastly, I also have a 16 year old dog who ALWAYS had the stinkiest GAS! OH MY GOSH! He could gag a buzzard on a dead fowl wagon! There were times our eyes would just water and you had to resort to mouth breathing if you stayed in the same room. I can honestly say he is now always welcome in the room with us. He still has gas because he's, well, and OLD dog
, (they are audible) *giggle* but they don't have the gag-factor! LOL