Do you by any chance take your car through the car wash? I've seen this kind of damage from bad brushes at a car wash, they get loaded with grit and just take the clear off the lights, they hit the tops and edges of the lights the most as they go over the hood. It happens over time and it's not apparent at first since the plastic takes a while to haze up once the clear coat is off. The biggest tell that this is clear coat damage is that it's on the area that gets the most sun and is the most exposed to car wash brushes and car wash damage.
I will let you know that headlight fix is only temporary. No offense, but all you did was buff and polish them. The problem lies in the clearcoat. I had the same problem with my old touring headlights. Notice how the "hazing" happens mostly on the upper area of the headlights, that's where the sun hits it the most. Headlight clear coating is a whole different material than the clear coat on the paint! It's much thinner and more easily damaged by abrasion. Polishing will remove the hazing and remove more clear and temporarily make it look better, but it will come back
The clearcoat that Mazda used on the headlight is not very good. The "hazing" that you buffed out, will return in a couple of months, how do I know this? Because I did the same. I had a detailer buff and polish the headlights and after a couple of months it returned.
There are only 2 ways to fix the issue, you either get new headlights, which is unlikely in your case, cause you have a GT or you take your headlight to an expert, have them wet sanded properly and then apply new quality clearcoat, this would fix them permanently or at least for a few years to come.
The haze is not a haze, but clearcoat failure just like it happens on paint and just like on paint, you can buff and polish the paint all you want, but that cleatcoat failure ain't going away until you sand, respray and apply new clearcoat
