Okay, I took a few leaves from my tomato plants down to the local garden center and the guy there told me it looks like late blight and that there's not much I can do about it at this point.

I had the blight last year and although on one hand this has a slight resemblence in the fact that it just looks like part of the plant dies (brown dried up leaves. On the other hand it doesn't in the fact that the upper half of the plants look very healthy aside from random affected leaves. I still have tons of blossoms, the fruit itself is unaffected.

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