Sorry for the double post.
Their are two possible reasons for singes on your leaf, i know that bud mentioned one.

But i knows thiers another. I'm not sure of what the second cause may be, Thats why i suggested those, but never really knew for sure which one, mabe it's even neither, but im pretty sure at least of of the 2 i used to know would be the reason. Mabe i'll remember tomorrow.

The C