Zucchini plant rotting stems
I have a zucchini plant that had been doing very well. It had 3 main stems. Yesterday I noticed that one part of one stem the leaves had shriveled up and that part was separated from the stalk and I pulled it off. This morning, one of the other entire stalks separated from it's base. The parts that separated appeared as if they rotted away, they were soft and mushy and a light brown color. I still have one base left that I just harvested a large zuke from and there is another one growing on that plant.
Any idea what causes this? Too much water, not enough sun? This plant is in a 10 gallon smart pot (fabric). It had just started to spill over the sides, it's it possible that the strain of the weight of the plant caused this? Will the stems that remain in the ground continue to grow? I'm afraid I've lost the leader and will get no more fruit.