Two more causes of fatigue are B12 and folate deficiencies. B12 is difficult to absorb and is best taken in sublingual (under the tongue) form. If we do not have sufficient hydrochloric acid or intrinsic factor, the B12 is not absorbed and can lead to anemia.

Folate is in high amounts in food like lentils. Folic acid is the synthetic form that could create health problems.
Here are some links:

Two things need to happen for your body to absorb vitamin B12 from the food you eat.

Hydrochloric acid in your stomach removes vitamin B12 from the food it was in.
Vitamin B12 combines with something called intrinsic factor, a protein made by your stomach.
Vitamin B12 is then able to be absorbed by your digestive system.
https://my.clevelandclinic.org/health/diseases/22831-vitamin-b12-deficiency
Folate-deficiency anemia is the lack of folic acid in the blood. Folic acid is a B vitamin that helps your body make red blood cells. If you don’t have enough red blood cells, you have anemia.

Red blood cells carry oxygen to all parts of your body. When you have anemia, your blood can’t bring enough oxygen to all your tissues and organs. Without enough oxygen, your body can’t work as well as it should.
https://www.hopkinsmedicine.org/health/conditions-and-diseases/folate-deficiency-anemia#:~:text=What%20is%20folate%2Ddeficiency%20anemia,all%20parts%20of%20your%20body.