You dont need to change formula from stage 1 to 2. Most of the stage 1 formula will be up till 1 years old = 12 months. Not necessary to make a switch. If every milk he/she poop then not acceptable. Its like adult, you eat you poo you hungry and you eat you poo you hungry. The pattern is the same.
stage 1 and stage 2 nutritional needs are different. I think should as long as not watery stools every pooing then it's fine x so long as baby gain weight and eat normally with no fussing. if you are concerned, tell the PD.
itsallabout_mytwokids