I came home from a long Memorial Day weekend and used our toilet. The toilet flushes and the tank fills properly to the appropriate levels but water constantly is streaming into the toilet bowl. I can't figure out how to get it to stop running. This toilet is only 4 years old. The only way to stop it from running is to turn of the water to the toilet. The water level in the bowl remains constant. It does not disappear and it does not increase. The water inside the bowl just runs. Any advice??

Thanks in advance.