Cucumber leaves - vein restricted spots - dying

[MlssaBuch]

It starts like this

Then it spreads more like this

Then the leaf starts to brown in large sections

Eventually dying like this. If the leaf is left on the vine it turns brown and crispy and the vine starts to yellow.

This is my first year gardening. My garden is organic. I have four 4x4 raised beds with Fox Farm soil as well as many container plants. I had no idea my plants would do so well, so I mistakenly crowded the bed of cucumbers. There are eight plants in one 4x4 bed. They are trellised on three sides up and out of the bed. Everything was going great and the plants fully matured and have been putting off tons of healthy tasty fruit. Then the leaves at the bottom started dying. I assumed it was overcrowding and maybe a mildew problem. I live in Georgia and it has been a very wet, hot, and humid summer. I cut back a lot of the underneath (dying) foliage and sprayed like crazy all over with organic fungicide/insecticide combo to kill powdery mildew and possible insects. It seemed to help a tiny bit.
After a week I noticed a lot more dying leaves at the base of the vines and it started spreading to higher up leaves. I sprayed again with a different fungicide that kills downy mildew instead of powdery. It didn't help at all. Then I considered a nutrient issue due to the overcrowding. Over the past 60 days I've fertilized using bone meal, epsom salt, and Fox Farm liquid Big Bloom and also Fox Farm Grow Big (Not all at the same time though).
The plants are continuing to turn yellow then brown on the lower sections, but still producing tons of cucumbers. I'm lost and have no idea what to try next. I have heart breakingly cut a ton of dying leaves trying to keep whatever this is from spreading. Also it seems to be attacking two or three of the vines/plants more than the others. There are a few vines/plants that don't seem to be affected at all. When I cut the vines and try the test of sticking the two cut pieces together and pulling them apart I don't see any sticky stringy goo in between them.
I haven't seen any cucumber beetles. The main two bugs I've seen are a few stink bugs and tons of Japanese beetles. The Japanese beetles are attacking the okra leaves but the okra is too big to be affected overall by them. I haven't seen any stink bugs on anything in the garden specifically, but I know they're out there because we seem them on the screen porch.
I water every other day by hand and use a hose with a wand only at the base of the plants. I never wet the foliage while watering. Yesterday I did a foliage feeding with epsom salt and a very mild liquid fertilizer. Haven't seen any difference yet, but it's only been 12 hours.
I'm sorry for the long post but I wanted to get all my base info out there to get the best, most informed, help from you guys! I'm lost and seeing my beautiful cucumbers die is driving me nuts!

[imafan26]

It looks like you have downy mildew. It is a difficult disease to control once it takes hold. The North Carolina has a publication on it. The pictures look like your leaves.

https://www.cals.ncsu.edu/plantpath/exte ... Mildew.htm

[rainbowgardener]

Agree, it does look like downy mildew. What do the undersides of the leaves look like? That is more diagnostic.

The pathogen, Pseudoperonospora cubensis, causes angular, chlorotic lesions on the foliage. These lesions appear angular because they are bound by leaf veins. During humid conditions, inspection of the underside of the leaf reveals gray-brown to purplish-black ‘down’. This is the sporulation of the pathogen.

https://www.cals.ncsu.edu/plantpath/exte ... Mildew.htm

Fungicides (whether organic or chemical) work better preventatively than when the disease is well established. Now that you know you have downy mildew in your garden, in future years you probably want to start spraying something fungicidal from the beginning of the season, every other week. And next time don't over-crowd! Conditions that favor development of fungal diseases include over-crowding and lack of air circulation, very humid, rainy summers like you have had, overhead watering that puts water on the leaves, excess nitrogen fertilization leading to lots of very tender leaves. It helps to mulch well to prevent soil splash back. Look for resistant strains.

You may or may not be able to save your plants now. Keep removing all diseased leaves. Best Wishes!

[MlssaBuch]

The underneath sides of the leaves look completely normal. That's why I wasn't sure if it was downy mildew or not. I haven't seen anything resembling any mildew, black, grey, purple, etc.. So keep cutting off infected leaves, keep spraying, and praying? LOL thank you guys for your help! It's not what I want to hear, but hey, thanks!

[imafan26]

I just found a neat thing on the NCSU site. Near the bottom of the publication is a link to a NOAA site tracking downy mildew progression in the U.S. Well for the majority of the U.S. Hawaii and Alaska are left out...again.

[MlssaBuch]

https://cdm.ipmpipe.org/current-forecast

This is a pretty useful map that shows the downy mildew forecast for the east coast.... no wonder it got me :/

[MlssaBuch]

NOW I'm NOT SO SURE IT'S MILDEW!! DANG IT.... look what I found now, huge pickleworm infestation. AWESOME

[imafan26]

Well you probably have both. That is the thing with distressed plants they just shout out to bugs to attack them. You need to net the plants or bag the fruit to keep the moths from laying eggs.