My question is how do you know it is your QL? There are a lot of structures in the same area. If it were merely a tight muscle then stretching over time will "fix" it as long as your activities don't ovruse it. Test the strength of your gluts doing 1 leg squats, kettlebellsg, 1 leg bridges etc. When you use both legs simaltaneously, the stronger leg will always dominate and use more. And yes a tight HS does not mean a strong HS. IT means there would be difficulties straightening your leg during a long stride. You have a mechanical issue and this involves movement patterns , joints, and yes muscles. Test it. I find it rare to merely be a muscle weakness. There is a lot going on with movement.
Test the movements. Which cause problems and which relieve it. Do you get lasting relief or pain after specific activities ? Are there postural asymmetries when you look in the mirror straight on?