Sounds like it could be some root rot- too much water/poor drainage? At least, this is what happened to my pumpkin vine and I called the county ag. extension and they said that it sounded like the plant had been in the ground too wet- I also have them in raised beds with mixed soil.
Before you turn on the soaker hose, stick your finger as far as it will reach into the soil just to see if only the top is dry and in fact there is moisture left farther down.
good luck,
christy

thanks Christy for the feed back. I'm pretty sure your are correct about the watering. I stuck my finger down 5-6 inches down and the soil was a soggy muck. I think I should have dug the hole deeper to help the drainage out since the natural soil is clay. I've changed my water settings and will post a follow up with the results.

this is what has happened to my plants too. What can I do? I cut back daily watering and went to every other day, no change.

Same problem withy tomatoes in containers.. Can't find anything about such thing online, but here I see the same problem people are/were dealing with. PLEASE if anyone knows the reason and how to help the plant, tell me what I could do.. I'm really worried if it is dangerous for my other plants. This brown thing covers the entire stem, not as much on the top though. And if I rub the stem with wet paper towel the towel becomes brownish.. Some lower leaves turn yellow. Slowly, t they do.