Dana has not been feeling well she gets fatigued easily and has difficulty focusing what type of deficiency might cause her condition

What is the question? If you are asking what could cause this, it could be many things such as dehydration, malnutrition, anemia, chronic fatigue syndrome, it could be that she has insomnia, she may not be going to bed early enough, etc.

If you want a more accurate answer please ask an actual question or add more details.