1) it is ok for baby not to poop everyday. Once in 2-3 days also ok, as long as baby poop not too hard and not constipated. Sometimes it's just not daily. U can consider adding a dash of water more to his milk 2) why don't u stick back to the one that worked for ur baby instead of re-finding something else? It could be a hit and miss. Hopefully u did not just suddenly make the switch caz babies will sometimes reject the taste - the transition has to be smooth. E.g. 4 scoop milk powder -- day 1 is 3 scoop A 1 scoop B; day 2 is 2 scoop A, 2 scoop B etc 3) base on baby age - u can see the health booklet. Some baby gain fast than other so it's hard to gauge too
How old is ur baby? Different baby suits different fm. So what suits other babies might not suits urs. I would switch back to NAN HA if I'm you. Otherwise I will just go around trying other Brands. By 4 Mths they should double their birth weight. Depending on age, bb growth n weight gain is not consistent
Different milk varies according to the child. Its not one milk suits all. I would switch back to Nan Ha. Whats the reason for changing the milk? Also it is okay if lo does not poop everyday.