Farm animals are also supplemented with b12. There is b12 in some algae but it is not reliable source and it is the only thing smart vegans should supplement. There is no RDA for EPA and DHA, just for ALA but you can buy algae derived EPA/DHA if you want. Just FYI, yes, brain is mostly DHA but DHA from supplements cant cross blood-brain barrier. For k2 the best source bay far is Natto which is fermented soy and it is in the form of mk7 which stays much longer in the blood thank mk4 form of k2 from animal sources. Other fermented veggies also have k2 but much less. D3 over the winter can be obtained buy eating sun dried mushrooms (i dried mine over the summer), yes plants are amazing and mushrooms make d2 and d2 vitamin in large quantities by drying them in the sun or under UV light. Etc, etc.. But in the end just look at vegan populations or plant based eating population and on average they live longer and healthier so they are not missing anything in the diet, not anything essential anyhow