Can You Identify the Cause of This Problem? *pics*

[dice]

Did you test pH to see if there was much difference between
afflicted and not afflicted plants? I was wondering about
flouride toxicity, which is more likely in low-pH soils. Plants
don't use flourine, but municipal water supplies usually have
a steady supply of it. A number of other minerals that the plant
usually has no problem with can become a problem at low
pH levels, like iron and magnesium, which become much more
soluble at low pH and may block the intake of other nutrients
that the plant needs or simply be taken up at toxic levels.

It could be something built up in the soil from the water:
flouride, chlorine, salt, etc, that affects some plants more
than others. It is interesting that the plant does not show
other nutrient deficiency symptoms, like purpling or bronzing
of the leaves, red tones, tip die-back, chlorosis, marginal
necrosis on the leaves, die-back of the growing tips, etc.
For leaves to just suddenly curl up and die without any
telltale color changes or other symptoms along the way is a
strange thing.

Maybe you will get lucky, and letting them dry out a bit will
fix it.

Edit:

PS: Since you have several affected plants, you could try a
couple of tablespoons of molasses in a gallon of water on
one of them, either adding it to the reservoir or just pouring
it on top of the container mix. The idea is to see if they are
running out of potassium, which is highly mobile in both
the soil and the plant. (Molasses is 5% potassium, and bacteria
break it down quickly.) The plant could be robbing the leaves
of potassium to ripen fruit.