I haven't grown this plant but googling indicates that a common disease is powdery mildew. You wrote that the leaves are getting whiter. Rather than losing the green in the leaf, could the "white" be mildew on top of the leaf?

Just in case, here's an article on the disease and ways to control/eliminate it. I saw pictures of a healthy plant and can certainly understand why you have it...it's a beauty.

http://www.growingagreenerworld.com/controlling-or-eliminating-powdery-mildew/

June

thanks but its not milder the actual leaf itself is turning whiter and then reddening, even the stems are reddish purple

Cold? Hot & dry? What's the weather like? Purple/red probably an indicator of the plant being stressed.

FataMorgana