When introducing a new stage of formula, it's generally best to do so gradually to allow your baby's digestive system to adjust. Instead of switching all feeds at once, try replacing just a few of the current stage feeds with the new stage formula. Observe your baby for any digestive discomfort or changes in stool. If they tolerate it well, you can slowly increase the number of feeds with the new stage over a few weeks. If any issues arise, you can temporarily revert to the previous stage or consult your pediatrician.