Hi there and welcome. No, this does not happen due to malnutrition, weight gain or stress. It is normal to have different colors of blood during a period. Brown and black blood is old blood. Most women have this during their period at some point. It comes out with the new blood. The vomiting could be a reaction to cramping. Some women do have nausea/vomiting as a pain reaction. Try to eat regularly and stay hydrated. Try ibuprofen. good luck
happens some time due to certain factors...malnutrition,weight gain or loss.stress..etc...dont worry