help fix over-nitrogen'ed buckets

[paradajky]

Over 8-weeks since transplant many of the plants are loaded with tomatoes, no abnormal growth! Very excited, the first tomatoes have begun blushing, too. Sadly, I've also spotted powdery mildew on a few vines, despite spraying weekly.

Interesting trend I'm seeing with the dwarf varieties, the lower leaves get sort of burnt/crunchy/withering looking. If I don't cut/break them off, eventually all the leaves on a stalk will wither up and the stalk just falls off on its own. Is this some sort of disease possibly?