Giving Econorm is absoleutly fine . You can give one ampoule / sachet per day for 5 days. You are right it may be some viral infection which should resolve by itself in 3-4 days. Keep a watch on urine output. If the baby is passing urine once in every 4 hours there ia nothing to worry about

If baby is passing adequate urine ie minimum 6-8 times per day Then no need to worry for motion Don't give so much importance to motion unless blood in motion or bad smelling motion Keep ur baby well hydrated Continue to give Breast milk Don't give water and other food items at this age Wait for some more days Everything will be alright If blood in stool or less urine output then consult with nearest pediatrician For now Give Liq. Enterogermina 5ml once a day  for 2 days only It will help.

Ya you can give...formulae milk can also cause green stools which is quite normal...but how is the consistency has to be assessed to say it is loose stools....