You might have a nematode problem. You can buy beneficial nematodes which you can add to your soil. They will consume any harmful nematodes which might be there. Do a Web search on nematodes. You can purchase a can of nematodes on-line.

Marigolds are supposed to be helpful for correcting nematode problems. They are also helpful for deterring insect pests. I have French marigolds planted throughout my large produce garden, as well as some lavender and santolina for pest control. Chrysanthemums also help to repel insect pests.

You might want to consider putting in a winter cover crop which will enrich your soil with nitrogen and minerals. Something which can be dug in come spring, as a green manure. Good luck!
Lorna

What is your soil in those planting boxes?
What is the soil pH of that soil?
How well does that soil hold moisture?
How well does that soil clump and how well does that soil fall apart, the tilth?
What does that soil smell like?
How much life is in that soil, earthworms?

Thank you Lorna. I will definitely look into the nematodes and marigolds. I have some lavendar growing but not in the infected boxes. I have looked into a winter cover crop and will be doing some research to see which ones are best for boxes. Your suggestions were very helpful.

Great questions kimmsr. I'll do my best to answer.
The soil I have is half store bought/organic soil from a nursery while the other half is compost from my composter.
I haven't tested my soil. I'll get one of those kits today. I promise. The soil holds moisture fairly well. The soil is in boxes, some long and narrow while others are rectangular or square. The soil falls apart when squeezed (when damp). The soil smells, hmmm.. hard to describe but mushrooomy. There actually is some weird fungi growing at different times of the year. Some that cover a large area others that are more like mushrooms or little cups.
Lots of red worms. I added them a few years ago and there is a good population. Hope these questions can help to discern what's going on in my boxes. Thanks so much for taking an interest. I would really, really like to grow cukes and beans again.

if the problem is nematodes, you'll see evidence on the roots. The nemas common in So Cal are root knot nematodes (RKN) which make small, irregular shaped bumps along the roots.

Then if it's RKN, the bit about "You can buy beneficial nematodes which you can add to your soil. They will consume any harmful nematodes which might be there" sounds good, but is a lot of wishful thinking.

As for using marigolds against RKN, you must have a solid planting for the entire season -- the result is that the nema population will be suppressd but not eradicated.

And yes, definitely use a winter cover crop which you'll dig into the soil. As with marigolds, doing so will suppress the nema population but not get rid of it.

So dig up a failed plant and look at the roots. If they're knobby with RKN, put transplants into the garden rather than seed directly into the beds.

Hi Jean001. Thanks for the comments. Well, it looks like I definitely have RKN. I saw many bumps on the roots when I took out the diseased plants. So, you don't think the beneficial namatodes work? Can they help a little? The cukes were transplants but the beans were planted as seeds. Do you recommend a special cover crop for boxes that will help the RKN? Thanks again.