It looks like there are several different things going on but one of them looks like "Yellow Vein Disease". That one thing kind of overrides all other issues. Sorry Here is a link that might be useful: Remedy for Yellow Vein Disease in Vegetable Plants

@ jean001a: >The plants removed from the garden - damping off. Some, me included, thought of Bacterial Wilt of Cucurbits, but I could not find neither striped or spotted cucumber beetle. >The 2 fruits. Lack of water. In my other post, Trellis for my cucumbers. missingtheobvious wrote: >About the yellow fruit: cukes can have that shape when there's inadequate pollination... It might be one or both reasons. >Plus, the yellowing = over-ripe and ill shut down production. Fortunately, the SAME plant with the yellow cuke, is STILL producing new cukes. @ t-bird: >slugs might indicate too much water.... I found a few snails BEFORE planting the cucumbers, while digging. I donâÂÂt think the cause of wilted cucumbers are the snails. Look at the cucumbers roots! Could a snail do that? >looks like you had the silver mulch over cardboard mulch? Maybe kept the root too wet for too long. Yep, maybe; anyway I plan to remove the mulch to see what is going on. > Sorry for the loss.....did any keep going? Yes, 12 out of 27 are still ok. Whatever the reason some cucumbers died, for me the mystery is: why only SOME plants died, when ALL the cucumbers received THE SAME treatment (watering, sun, etc.) Here are two pictures, the first was taken when I planted the cucumbers, when ALL were ok, the second, today, after over half - 15 out of 27 - died.

Mine have had the same problem. It is caused by a sucking insect or mite which I have not been able to identify. I tried spraying with insecticidal soap to no avail, but then found an on line article suggesting the use of a systemic insecticide such as the one made by Ortho (formerly called Orthene). The treatment is to spray weekly for 4 weeks. I just sprayed for the 3rd time and my lantanas are coming back great. I don't promote the use of insecticides, but this is the only thing I have found that will control the problem. Just be careful with the spray.

I also think it looks like canker. The organisms that cause canker are around all the time and enter through the "skin" of a plant when it is injured, cold can cause injury so that spring is a common time to see canker damage. If the canker encircles the stem, all nutrients are cut off and the stem above the canker dies. If the canker does not encircles the stem, then it should recover. I agree that pith will show if the stem is alive or not, but you must cut off the stem off to see the pith, it is that corky stuff in the middle of a stem, but now the cane is dead for sure. You can check for life under the bark with the scratch test, and as long as there is green under the brown, there is hope. It can be false hope because the stem could have died below where you scraped and the top of the stem as yet to die, that's why a stem can continue to produce foliage for a short time even after it is dead lower down. In my experience, you can kill a weak plant by pruning off all the canker damaged stems, when if you just left it alone, it be would be ok. You can always prune the stem later if it dies, If it is a vigorous plant then pruning it won't hurt, do clean your cutters after each cut. You do not want to spread it to healthy wood.