My rescue cat takes Viralys for control of Herpes which helped the symptoms but now has stools which are formed at first but then it changes to loose consistency with bright red blood. His stools are every other day. Other than that he has lots of energy and seems healthy. I feed him chicken once a day and have Purina One sensitive, urinary tract, and hairball formula mix available to him all the time. What can cause the abnormal stools and what can I do to correct this before I take him to the vet?