Red Lettice is not red

[Dennis Schneider]

My Red Lettice starts with a little red, But when its fully grown no red at all. Could there be something missing from the water?

[Eddie Beuerlein]

Are you growing indoors or outside?

[Dennis Schneider]

In a half shed greenhouse

[Eddie Beuerlein]

Do you know the exact name of the lettuce variety? What temps are high/low in greenhouse? Environmental factors can influence the color of lettuce.