Tonette,

I had a problem like that sort of thing with my Onc's at one time. Turned
out to be fungus in my case. Of course, I can't tell you for sure, but it
wouldn't hurt to give it a shot of natural fungicide. Go to Ray's site for
recipes:

http://www.firstrays.com

Also, is it possible that the plant is getting a bit too much sun?

Diana