[Dynsei]

A lot of it could be from lack of iodine. Your diet is vegan, and iodine comes from sea products. 2 vegan compatible sources of iodine are seaweed and iodized salt. There might be another source of iodine, that isn't from the sea (I don't remember if it was pistachios, kale or cashews). However, you shouldn't overdo iodine, because the symptoms and other problems from too much are similar to too little iodine on the thyroid. Those who live far from the sea also typically have low amounts of iodine. It used to be common for those with large thyroids to typically live farther from the sea (because their thyroid expands to try to get all the iodine available, when there is little).

Also, it is important to get good amounts of lettered vitamins. They help prolong body tissue and health. For Vitamins A through K, 100% of the daily value, on average, is the minimum amount needed for optimal health.

For Minerals, those are easy to imbalance, so you must get those mostly from food, except for B12. You can take a multivitamin. If you want, you can take  a combination of lettered vitamins, and a calcium/magnesium/Vitamin D supplement to help,. But try to avoid individual mineral supplements (except B12), because those are hard to balance, when they must be balanced in proportion to other minerals. If you're worried about supplementing with minerals, ask your doctor. Vitamins (A - K) don't imbalance so easily, because with them, the only way to imbalance is either having too little or too much, except for synthetic vitamin A, which typically isn't good. Pro or pre-vitamin A in high amounts is perfectly good.

A vitamin you may be lacking is B12, because there are no significant vegan sources for it, except supplements. Bacteria produces vitamin B12. Cheese and Eggs are a vegetarian source for B12.