It may be the cucumber mosaic virus, and if it is, there's no treatment.

Here is a link that might be useful: Mosaic fact sheet

ugh .. though the pictures of yellow leaves on that page don't look like what I have. (they show wild pokeweed leaves, not cucumber). Also the tomato plants next to the cucumber share the aphids. (We couldn't control aphids very well :( )) Roma tomato has some dying leaves, not sure if its the same problem .. but cherry tomato seems to be doing fine.

Cucumbers are very yellow plants, whether in-ground or containers....they just seem to
do that. My plants are green currently, but they'll yellow as their season comes to a close.
Can you give us some indication of your fertilizing habits?

Josh

I don't know what it is but yes, they are dying. The same thing happened to the plants in my Earthtainer last month. I was really disappointed since they started out so well.

You would probably do best to pull out the cucumbers and focus on keeping the rest of the plants healthy.

greenman .. I have created this container using 3:2:1 mix and made a fertilizer strip. (using garden tone by epsoma). When the leaves started yellowing, I replenished the fert strip. (I have used same amount as specified in the earthtainer document)

Athenian .. All my cukes (in two separate locations separated by about 30 ft) have this same problem .. So if they are dying, I will enjoy whatever few cukes are left and think about getting more disease resistant type next year :(

I don't think that your plants have mosaic. I don't see the patterned leaves or yellow leaf veins. I think that your plants just are old and maybe filled up their containers, and the roots had no where else to go, and so the bottom leaves are dropping so the roots that are there can support the leaves that are new. How big are the containers, and how many plants do you have in each? How long have they been growing? Has it been cooler, or warmer lately? Wetter or drier than usual?

I haven't grown a lot of vegs in containers, but of the cukes I have in the ground the oldest leaves on the slicer are getting not yellow but sort of dried looking, and it is cooler so the production is dropping a bit. I expect this to continue until frost. The pickler was a "bush" variety, and it seems to have just reached a stopping point and is kind of giving up. That's okay, I have enough pickles.

Not sure about the brown flowers. There are some mildews that attack cucumbers, but you don't have any of the leaf symptoms. (The leaves would get more and more spotty-brown, and you could see the spore cases on the underneath side) Did you let them get a bit too dry once, and the those flowers aborted? That can happen. If it got really dry for a long time, then the roots can get damaged and the plant can't really recover that well from that. Seems like you would have more crispy leaf damage in that case.

Really though, cukes don't seem to last forever, like greenman said. Did you get a good harvest? I could see you still had a cuke on your plant.

As Josh pointed out, this is very common for our area as summer comes to an end. They are all worn out and the cukes themselves take all the nutrients from the main plant.

Be happy you got something. The dreaded 'powdery mildew' got all mine along with earwigs which has been an unusually high problem this year with the lack of rain all summer, then high humidity, then very dry weather. It has been a killer for mine. The mold spores are very high and everyone I know growing cukes lost theirs to the same thing.
Now, if your cukes died from some sort of disease, then I would suggest you pull them out and burn them or toss them away, far away. Rake that area very well and do not plant them in the same location next year.
if you do, them make sure to take a leaf or two to your local nursery at first onset and get treatment for it before it happens again.

Mike

ASeedIsAPromise: This is big container 4'x3'. The grow media (raybo 3:2:1 mix) is 13" deep. There are 4 pickling cukes, 2 tomatos, 1 pepper, 1 eggplant and 3 herbs (basil, mint, thyme) in there. (somewhat crowded). All have been growing in that container since May 17th. Here in new england, I think the summer has not been unusual. This is the first year of growing vegetables for me, so I don't have any frame of reference, but between the 6 cuke plants I got around 70-80 pickling cukes in one month. (And there are still about 15-20 cukelings on the plants). We are very happy with what we got so far.
The flowers drying/dying/rotting is troubling though. Is that a disease? I am also seeing rotten flowers on roma tomato now (which is next to the cucumbers ..) If they die this year .. fine, but I need to learn what went wrong so I can may be improve next year .. After strong and steady rain, the flowers died .. but it may not have any causality.
The container has a water reservoir at the bottom and it never went dry. I have a float mechanism and I always refilled the reservoir after it was half empty.

Mike:
The summer didn't seem that different this year in new england .. (though there were spells of humid air, dry weather, high heat etc). So Cukes are not expected to produce until fall? We are 2/3rds into the summer. I was hoping to get another month of cukes :)

When I plant in the ground, I put one or maybe two cukes in a 4 X 4 area.(They grow up a fence) I have gone out and picked 20 cukes at a time every couple of days. I am swimming in cukes. If I had 4 or 6 cucumber plants I would have to go out and cultivate a whole lot more friends! :) Also I leave 4 X 4 for a tomato plant. Peppers and eggplant get about 3 X 2 or 3 X 3 for each plant. Do you see where I am going with this? You have a lot of plants in a small space. This leaves less room for roots, and so your plants are going to not grow as well, yield as much and/or be more susceptible to disease. If the plant can't support making another tomato, then it will abort the flower. If you did something differently next year I would put fewer plants in the space.

Yup .. I will be reducing the number of plants in that container next year. (I will be building few more containers .. so I should be able to have at least the same plants in 3 times the area .. )

I think that what I have resembles gray mold. ( botrytis mold ) I saw a stem legion on couple of plants :(
Here is a closer picture of one of the cucumber flowers ..

Molds are common where it is humid and where there isn't much air circulation around plants. It is common in greenhouses, for example. If you have botrytis then next year I would leave more space around my plants and try to separate the containers to encourage air movement. Don't go out and harvest or work with your plants when they are wet. Collect and destroy all infected debris as it occurs. Wash your hands and tools between working with an infected plant and working with a clean one. Rotating crops won't really help with botrytis, since it likes everything.

Update!

I spent a few hours removing all the gray mold from cukes at one location. (Left the cukes at the second location as they were for control and because it was taking way too much time). Continued to monitor and remove gray mold daily for next week. Cuke plants are doing much better. There are lots of new cuke flowers. Funny thing is though there are very few male flowers, so hand pollinating has become very difficult. There is less than one male flower per two female flowers. I am guessing that gray mold attacks male flowers more easily and I removed most of those to remove the gray mold!
The location where I did not remove the mold, the leaves have further yellowed and the cukes are pretty much dead.

Lessons for next year: reduce the crowding and watch and remove such mold as soon as it appears.