I advise you to, in case the stool consistency does not become less watery within a few days:

1- Perform a stool analysis, culture, and Rotavirus antigen just to make sure that there is no actual infection, though I doubt it will be positive, but it is appropriate to do it at that stage

2- Go back to using Nursie 2 for a while, then gradually introduce Nursie 3. So for example, give 1 out of 4 bottle of milk of Nursie 3, the rest of Nursie 2, and increase the number of bottles of Nursie 3 if your child tolerates it (meaning, no loose or watery stools).