Hi and welcome to the forum! I am glad that I can help you.
You want to know the cause of the symptoms that your husband experiences.
Individuals usually defecate every day or every other day. If individuals defecate more than twice a day, and the stool is watery, they may experience diarrhea. If there is another change of the stool such as the presence of mucous, pus, or blood, it may indicate that there is alimentary infection. There is another medical condition called irritable bowel syndrome that is characterized by predominance of diarrhea or constipation, and which diagnosis is based upon excluding all the other common conditions with similar symptoms.
Given the symptoms that you described, your husband experiences diarrhea. He may consider having a bacterial culture with an antibiogram from a stool sample to rule out possible bacterial infection. He may also consider having his stool checked for possible parasitic infection. He may also want to avoid consumption of sweet food or artificial sweeteners because sugar may cause diarrhea. He may consider seeing a gastroentelogist for further diagnosis.
Please keep in mind that I provide medical information only. I am not able to diagnose medical conditions online. Please advise your husband to contact his doctor or other qualified healthcare provider such as a gastroenterologist for further advice and information about diagnosis and treatment options.