I strongly suggest getting vitamin D checked, but that doesn;t pertain to vegans only. there are vegan D3 now made with lichens
Thats all if you eat a well balanced plant based diet
I also take algae DHA. I tried it several years ago and found it absolutely gave me better attention and focus, so I continue to take it-theoretically we should convert what's in plant fatty acids to DHA--found only in sea foods, either fish oil or the algae fish eat--but not everyone seems to do it well
“Specific recommendations for a healthy diet include: eating more fruit, vegetables, legumes, nuts and grains; cutting down on salt, sugar and fats. It is also advisable to choose unsaturated fats, instead of saturated fats and towards the elimination of trans-fatty acids."
- United Nations' World Health Organization