HI, thanks for using healthcare magic It is possible that it is related to diet or infection, it may not indicate candida infection because this is not very common. The most common infections of the gastrointestinal tract are viral or bacterial infection. It is good that he enjoys fruits and vegetables but as you indicated, he would need to increase protein if he uses only very little. Protein could be from plants or animal but it would be a very important part of any balanced diet particularly a child, many essential amino acids come from proteins. An important part of management of diarrhea or/and vomiting is fluid management. You need to make sure he takes enough fluids to prevent or treat dehydration. I hope this helps