"James" wrote in message
...

[snip]
Within a week, some of the leaves on the plants
started turning yellow, and within 2 weeks many leaves are brown and are
falling off. These plants will be dead in another two weeks. This is
baffling to me.

From trying to research on the internet, I believe I could be seeing
chlorosis, resulting from iron deficiency. [snip]

--James--

From your description, I don't think your plants are dieing from lack of
fertilizer or iron deficiency. That would be a long-term process with your
plants gradually losing vigor and deteriorating.

It sounds to me like there is something active which is killing your plants.
Possible considerations:

Soil contamination with a herbicide
Grossly excessive water
Salt contamination

Without knowing where you live I can't do more than suggest you look in
these areas, but consider what may have happened in your area in the period
just before your plants started dieing a year ago.

Does your water softener now drain into the planted areas?
Did you or a neighbor do something that drastically changed the way
rainwater flows around your property?
Was something spilled, such as gasoline, paint, herbicides?
Did you use a lot of salt to clean your walkway, which got shoveled over
your plantings?
Did you pressure clean your walk or house with a commercial product that
includes bleach?
Did you apply a mold-killer to your walkway or siding?

Also, scrape away some of the mulch and probe through the first 12" of dirt
to see how moist it is. If you're in a clay area and watering regularly you
may be flooding your plants underneath the mulch. Good luck, and let us
know what results you get -- Regards