tomato leaves blackening
A few of my tomato plants have many branches of blackened leaves, and some have shriveled up completely. I've stripped the plants of those branches. I'm attaching a photo of the leaves and the full plant. If you zoom in you can see black spots on the stem. I also have a few plants with yellowing leaves--just attached a photo of one of those branches, but not the entire plant, which looks otherwise ok. It looks like a kind of fungus. With the wet weather, I'm guessing that's likely. I have raised beds with a pool liner on the bottom, and wood chips to on the bottom 6" layer. There is a drain for overflow before the soil layer. It worked very well last year, but with all the wet this year, I'm wondering if it's too moist and if I should widen the overflow drain. I'm also wondering if I should just pull those plants out and start again.
Montgomery County Maryland
This sort of thing (the blackening edges) seems to be an issue with too much water or too much fertilizer. It is not a disease but rather some kind of osmotic issue in the roots, i.e., too much water and some cultivars react to it with necrotic tissue developing at leaf margins.
Why the pool liner? Sand would be a better choice than woodchips for drainage. Once the chips become waterlogged, they often can swell and form more of a barrier to water infiltration. The beds will drain, just not very fast with lots of frequent and heavy rains.