We just repaired an intermittent leak in our toilet by replacing the flush valve. In doing this I noticed a couple connections that could cause a leak.
First, if the connection between the water supply line and the toilet is not properly seated, it could leak. The plastic female connector attached to the hose could leak, especially if deformed, not tight or under stress. Some Teflon tape might help this connection.
Second, the hose that connects the flush valve to the toilet bowl has an O ring that if not properly seated in its groove, could leak. With a new toilet, I would doubt that this was your problem.
I would suggest wrapping the hose with paper to narrow down where the leak originates. You might also have a small crack in the pipe.