Child Started Vomiting After Eating. Having Fever, Diarrhoea, Feels Tired And Nausea, White Stool. What's Wrong?

My 1 yo son, had episodes of vomiting couple of hours after eating dinner at restaurant, no initial fever, had diarrhea the next day. another episode of vomiting the next day while playing outside w/ his brother. his 4 yo brother who had no previous s/sx the previous day had couple of episodes of vomiting, fever and dirrhea the same night. he felt lousy for the next day (tired, nausea ) his fever subsided the following day and he felt better. the third day our 1 yo son continued to have diarrhea. His baby sitter had the same symptoms (n/v, diarrhea) at the end of her shift. she feels better now after 2 days. My 1 yo is still has no appetite ( normally very good appetite), still w/ white stool and not his usual self. I need your help.