Can I use LED bulbs for my headlights?

Can you put LEDs in, yes. Should you, No. Why? First there are no street legal LED conversion bulbs or kits on the market. That is because of the laws that automakers need to follow to get a car legal. They have to have each system on the car accepted by the government before it can be used on the street. Part of that is getting the headlamps systems approved. Under that approval if a car was built with halogen lighting you legally cannot swap in HID or LED. The other reason is that LEDS are a different light source type. In a Halogen there is a long filament that stretches between the posts inside the lamp. It radiates light all around it and across it. The lens and reflector in the vehicle is designed to capture and align that light so it is an even light that can be focused as needed. An LED on the other hand is a point light source. Instead of a wide filament of light it is small pinheaded spots that give off light. The problem then becomes that the reflector cannot capture and focus that light into a usable beam. You end up with a glare that bothers oncoming drivers because the light bounces around the reflector at random. The lights seem brighter from behind because they are not focused and they light up more of the area around the light. Sort of like driving in snow or fog where your headlights reflect back at you. At the same time the light, out the front isn't aligned so you don't get a working high or low beam.
Then there are also the issues with the vehicles electronics. Because many of the LEDs out there are of low quality, they cause issues with the vehicle itself. Odd codes or very unexpected operation from the way they are made causes problems.

I generally use Sylvania Silverstar or Phillips Crystal Vision bulbs in vehicles that need better light from stock lamps. The drawback to those bulbs is a shorter lifespan generally. That is because to get the brighter lights the filament has to run hotter to generate the brighter light. You noted that you changed them a while back and they were brighter, that is also common with halogen lights their output gets lower as they age. Because of where I live and when my wife travels her car gets new bulbs every other year. Partly for brightness but also to combat the poor headlamp design on her car. Looking at the Sedan and the Note lighting, both look a bit underwhelming in design, similar to many modern vehicles. What I might do if the car were mine would be to change out the bulbs and look at adding a small LED light bar under the face of the bumper that uses a relay to turn on with the high beams.
For low beam operation see if you can add fog lights under the bumper.