Yellowing leaves with brown/rust patch

I returned from being gone for the weekend to find my Nugget looking very ill and the Cascade beginning to show the same symptoms. I haven't seen this issue before, anyone have any ideas?

Leaves are yelling with large areas of brown/rust colour. This basically occurred within the last two days as they looked fine on Friday. The following are two photos of the problem:

Lower half of Nugget

Close-up of Leaf

Fungus? Deficiency?

These are second year hop plants that had been doing very well up until now.

Because I can't find anything to suggest differently, I'm thinking water (extremely wet or very dry) or nitrogen or iron (or any combination of the three).

My cascade is showing similar signs. Check out this link, looks like Nitrogen deficiency

http://www.freshops.com/hop-growing/hop-diseases-and-pests