helianthus leaves
 

One of the girls I work with has planted some helianthus and is worried
because some of the bottom leaves are turning yellow & brown & red. I've
never grown these and didn't find anything with my first search, so it's
time to publicize the question. Does this sound ok? I'm wondering about
mildewy things, maybe related to the recent downpours. ??

Thanks

Arwen