Headlight cleaning

My headlights have gone a bit yellow in places but the feel smooth on the outside which makes me think its on the inside. Please see the photos and advise if inside or outside and how best to clean them.
 

Attachments

  • 20220502_095206.jpg
    20220502_095206.jpg
    1.1 MB · Views: 27
  • 20220502_095213.jpg
    20220502_095213.jpg
    1.1 MB · Views: 28
  • 20220502_095220.jpg
    20220502_095220.jpg
    1.1 MB · Views: 26
Yeah, front end takes a hammering...I used a clay bar to get the grime out then sand, polish, protect etc.