I understand your concerns. Green stools are most often due to increased gastrocolic reflux. Formula feeds do sometimes results in green stools but mucoid stools is a concern. You can continue probiotics for another three days. I would recommend to stop formula feeds and give him breast milk for 6 months as American academy of pediatrics recommends. When you introduce new feeds that baby’s gut takes time to get primed to it. So passing 2 to 3 times a day is not alarming. Weight gain is also optimal.
Next Steps
If symptoms persists after these measures , please write back and you might need to add drugs to the baby.
Health Tips
Stop formula feeds
Exclusive breast feeding
Vitamin D drops.