How do I fix the headlights on my 2015 SRX Cadillac

Dullness? You mean the lenses are foggy? Seek a local detail shop near you, they may be able to "restore" them. Make sure you have original bulbs in there, not some kind of retrofit bulbs. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops