put some food coloring into the tank and do a flush. See if the leak is actually coming from above and showing up on the floor. If the wax ring and horn have a good fit, then its the rubber washers holding the tank to the base or that horn in the fittings, or its the hoses not fully tightened or last but not least, it could be condensation.
Tonight add some more food coloring to the tank and in the morning see what you can see. If its from above, the food coloring will leave a water running trail.