Buds3 very quiet on the left side

Hello, i have a problem. I mainly use my buds when working out or going for a run, which I thought wouldn't be a problem since they are supposed to be waterproof. Now the left side is way quieter than my right side, even when moving the sound to the left. They are not dirty or look any different than the right side. I've also tried resetting them, which also didn't help one bit. Since I still like to listen to music while training, I've wanted to use my brothers buds3 and while using them for the first time, the same thing happened. They're also pretty new. They are about 5 to 6 months old. Does anyone have an idea to fix this or know what the best thing I can do is? Any help would be appreciated. Thanks!