Simplify the following text for a Grade 12 native English-speaking person.
Original: Symptoms of beriberi include severe lethargy and fatigue , together with complications affecting the cardiovascular , nervous , muscular , and gastrointestinal systems .
Simplified: Symptoms of beriberi include severe lethargy and tiredness . There are also problems that affect the cardiovascular system , the nervous system , muscles , and gastrointestinal systems .