Squash borers will come. I always take part of the vine further down the plant and root it. Giving it more rooting points along the vine seems to keep production away from die back. I sometimes just cut the infected part away once I know the plant has additional roots. Literally, just mound up a little dirt over any part of the vine and it will take care of itself. It wants to live, too. I've got borers--but more squash than we can eat, so I just get over the appearance of the vines. (We also perpetually have white mildew from our humidity). Last year I had considerable cucumber die back, but not until I canned three batches of cucumbers. For me---the earlier you get the squash in the ground, the better off you are to beat the bug attack. Then, when it comes, it is too hot, I've gotten all the harvest I can handle and my friends are sick of my food, too, and I'm ready for the break the die back gives me.

Update on my chard. I now know that what was happening to my chard is called Damping Off and it's caused by a fungus attacking them. Makes sense, knowing what I know now about growing in containers. I tried sand too though and it did not work. Water still isn't draining even with the sand. I suspect that the "sand" I used from my yard is actually still filled with clay and I just didn't know it... I also tried 90% potting mix to 10% garden soil and that didn't work either. Then I tried 100% potting mix and it still didn't work...plants died from Damping Off, but they were outdoors in water-holding pots and we got lots of heavy rain...I guess they need to be sheltered? These little guys are so delicate...the heavy rain really compacted the potting mix... Been trying since...well, since Jan 2015...with little success.

Another plant death has fallen upon my household. This time it was my precious little plant that has been miraculously been growing well for almost half a year. The day before yesterday it just suddenly started wilting and the bottom of its stem started turning brown and woody, and now today I've noticed that the water under it's self watering pot has stop going down. Another death to my hands... and I was so proud of this one. Its the highest plant I've ever grown and now it's just dying before my eyes. I don't think I can save this one. I'm gonna miss u planty ;_;

It is possible you have Early Blight. Mine do the same thing. They will be fine until the first full day of high heat and humidity then it just explodes. The first thing to do is get all the bottom leaves trimmed off - I've read that it is fine to take everything off at least the first foot of your plants and even up to 18". Get them in the trash then wash your shears and gloves with bleach. This will help stop the spread. Copper fungicide or Daconil sprays, or Epsom Salt drenches are usual recommendations. I usually start spraying mine about 2 weeks after planting. Good luck with yours.