Hi. Thanks for your query. Noted the history about your 6 year old, vomited in the middle of night, , smelly egg farts and diarrhea. Similar things started with your 4 year old one. With the history you have provided, the possibilities are: There is infection through either the food brought from outside or old stale food or the drinking water or so. I would advise for both your children the following: Take them to the Pediatrician for clinical evaluation, examination and investigations to know the severity of the gastroenteritis they are suffering. If not severe, they will be given oral treatment. If much severe, get them admitted for intra-venous fluids, antibiotics and replacement of the electrolytes till they are cured. Secondly, find the course of an infection and also watch if the problems develop in the family to get treated in time.