If you are facing a low sound in your earbuds : 

• Ensure volume is set to maximum through Mobile Phone and ear buds both
• Use suitable size of eartips
• Use other music APP/music player as different songs/videos app have different audio quality with different Mobile Phones
• Ensure cleaning of eartips. Request you to clean it careful & to not use any sharp object to clean ear tips. It may damage the sound mesh.