After feed stool is normal called Gastrocolic reflex in this age group . More over this toddler age group child have stool called toddler diarrhoea often contain mucus and undigested food particle , it is due to relative immaturityof Intestine / Gut . Measure weight height of the child if that is normal ( u can document it from growth chart ) , then relax nothing to worry about

Stop outside  milk. Just see wat new diet was introduced ,stop all forms of sugars including outside juices

It can be normal if he had some form of laxative type of food. Anyways if this continues see your pediatrician to examine the child. As long as he is active playfull and passing urine you don't need to worry