My finch has been suffering from diarrhea for the last two weeks or so. We separated him from  others and stopped giving him fruits and vegetables, but to no avail. He's active but his body droops forward when resting. The droppings are very watery and slightly yellowish at times. He's also drinking a lot more water than usual. We disinfect the cage and change their food and water regularly, so not sure why this is happening. Please help, as the only avian vet in the district is no longer here.