The word Tú (you), which is written in brackets, is optional in all of the cases. Perhaps the literal translations from Spanish into English make few or no sense, but in Spanish they are correct.
(Tú) iluminas cada día: You brighten each day
(Tú) iluminas mi día : You brighten my days
(Tú) iluminas mi vida : You brighten my life
(Tú) iluminas todos mis días : You brighten all my days.

Hope it helps!

Antonio Muñoz G.
México, DF

Also, iluminas mi vida. Eres el sol de mi vida. It's more romantic to say "mi vida" than "cada uno de mis días".

Another suggestion

Your gaze is my sunrise.


C'mon Eric, pull out all the stops.

Iluminas cada uno de mis días