Thank you for your query,
may be of Viral cause. But the reconstitution of formula feeding and the hygienic feeding of formula should be rechecked as improper dilution and unsterilized bottle feeding will cause Gastroenteritis.
frequently and you can give probiotic like lactobacillus
sachets orally in prescribed dosage. Look for signs of dehydration and consult your Pediatrician
if loose stools are continuing or hydration decreases.
Hope i have answered your query.