Is your feeding enough for the baby because some times mothers milk is not enough for the baby and if your giving formula milk then go for Aptamil gold formula milk which is good for babies gut health issues as it contains HMO and prebiotics which helps baby in easy digestion to pass the easy stool

Exclusive breastfeeding is advised. mom needs to take good amount of liquids too.

It could be due to the food mother is consuming. Ask the mother to add prebiotics in her diet. This will help her with stool issue.

this could be due to less feeding intake. you can do a tummy massage which will help her and this will work in her favour