1- Your first two links are about VEGETARIANS, not VEGANS.
Shocking... People who eat vegetarian junk-food are less healthy than people who eat healthier vegetarian food. Who could've guessed...?
"They examined the effects of three different types of ‘vegetarian’ diets: one which emphasized plants but included some meat, a healthy vegetarian diet consisting of whole grains, fresh fruit and vegetables and an unhealthy version."
So, the study included "vegetarians" who eat meat??? And you think that applies to vegans???
2- A study from 2009 that may have raised relevant concerns at the time, but newer research leaves it in the dustbin. Without citing hundreds of newer studies, I'll just point you to the Position of the American Dietetic Association: vegetarian [including vegan] diets - https://www.ncbi.nlm.nih.gov/pubmed/19562864/
“It is the position of the American Dietetic Association that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian [including vegan] diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes.”
The American Dietetic Association's position paper includes 204 references. I think they researched it better than you did, before stating a position on it.
3rd link - A sensationalist tv show made sensationalist claims about kids on a vegan diet. In conclusion, the article you cited notes the same source I noted above, the Position of the American Dietetic Association.
I know more and more vegan "lifers", who have been vegan since conception. Without exception, they're among the smartest, healthiest, most socially well adjusted kids (and now adults, too) I've ever met.
About once a year, give or take, it makes international headlines when a kid is starved to death by clinically insane parents who claim to be following a "vegan" diet. In many cases, the diet isn't vegan, and in all of these cases the parents are just loons. But it's sensational, so it's news. Meanwhile... Childrens hospital in every city in every modern country treats millions of kids each year for malnutrition, and none of them are vegan. But that's not news, that's just statistics.