My Daughter Has Low Potassium, Dizzy After Eating Lunch, Irregular

My daughter has low potassium, dizzy after eating lunch, irregular heart rhythm it skips beats, some blurred vision but not each time, weak, ekg checks out fine, blood pressure is low 86/50, pulse in the 60's, athletic, otherwise healthy, celiac, 5'4" weighs 104. We have been to ER, family practice dr, and had blood work done. Everything but potassium seems normal. Have not had a fasting blood sugar