I bought my kitten about five weeks ago. He eats royal canine kitten food. The first few weeks he was doing great. His stools were solid. Then all of a sudden he started to vomit and have diahareah. I took him to the vet . He was negative for parasites. However they said he showed a slight titer for corona virus,but does not have FIP. They put him on Metronidazole liquid for 5days. Today is day 4 on the medication, he is no longer vomiting, however his stools still not firmed up. What is wrong with my kitten?