Okay, I baby sat a child that age, and she had the SAME problems.
AND so, she had, developmental delays and issues... and it did not get better. I babysat her until she was about 2 years old.
She also, by the time she was 6 months old, had to go to the Emergency Room, TWICE, for dehydration. (this is not normal).
Because, she would not or could not, or was not, fed enough.... breastmilk or Formula.
The Mom, would ONLY give me, one 4 oz. bottle of pumped milk, for the ENTIRE day. Then she'd tell me her baby was fine... just a tiny eater.
Duh. That is totally wrong and dysfunctional.
AND her baby, would throw up too.
For no reason.
This baby would also not give hunger cues, as a baby normally does.
This baby was tiny too. But was not premature.
They were just dysfunctional parents. I told them many times, of my concerns and backed it up with factual articles. They didn't do ANYTHING about it.
They took care of their pet dog, better than their own baby.
I almost called CPS.
But while she was in my care, she got attention and as much help as I could do. And I would, give her Formula. Since the Mom, even if I asked, would not give me more bottles of Breastmilk.
Now the fact that that baby you watch, has a Vietnamese Mom... is irrelevant. MANY parents, may think, that whole idea of "we have to fatten up the baby...." kind of mentality. Even in the USA, people still think this way.
Again, the baby does not have normal, intake or eating.
The baby I babysat, was basically malnourished. And if a baby is malnourished and it does not improve, then the developmental delays... becomes almost permanent. Or very hard to turn around.
A baby's primary source of nutrition, for the 1st year of life, per our Pediatrician, is Breastmlk or Formula. NOT solids and NOT other liquids. Solids, does NOT have, as much nutrients nor is as nutrient dense, as Formula or breastmilk.
Their baby is probably so lacking... because he is not fed, adequately.
That is why, he is that way.
They need to get medical, advise.
For the baby I watched, her parents NEVER told their Pediatrician, at all. I would ask them point blank.
AND I saw their child's baby book, from the Doctor... with her weight and growth percentiles. And comments. They kept it in the diaper bag.
If he is refusing the bottle... perhaps he does not even know how to suck? Or he does not know how, to feed? This can also happen.
Or they have given him a hang-up about it.
In any case, this is really... not balanced.