white leaves?

Some of the bottom leaves on a couple of my plants have turned white, and I was wondering why that could be? The plants are healthy otherwise, and the leaves that have turned white are still alive. I was wondering if anybody else had come across a problem lie this, and if so what you did to fix it. Thanks you.

Dane

Can you put up pics ?

could be mold

i have seen this... do the leafs feel like paper??

Are they white white, or like a pale yellow just not green kind of white?