Oh dear. I had a feeling homeschooling would crop up somewhere. Isn't it also utterly illegal in much of the EU, Germany, for example?
Vegans do need to take Vitamin B12. I was vegan for six months and took it daily, but I've never heard of vegans with a vitamin A deficiency. I am also one of those who bf my daughter almost exclusively for nine months plus, but I wasn't vegan or even vegetarian at the time.
Rickets is still quite common in exclusively bf babies in areas that don't get much sunlight - in the mountains of Iran, for instance, though anywhere north of Watford Gap means that even an hour of full-body exposure in winter won't do it - you have to take D2, and if you aren't told to while bf there can be problems; rickets is on the increase, alas, though bf is unlikely to be the main reason. This is because bf and winter alike deplete the body's stores of Vitamin D so that the mother runs out of it in early spring - now, in fact, so take some cod liver oil, ladies. Calcium is less likely to be depleted.
The case I remember from the US was a toddler put on a macrobiotic diet - she died of protein-fat deficiency, which became known as muesli malnutrition, somewhat ludicrously.