Post a pic.

What specific soil mix are you using?
I've seen all manner of mix described as 'well-draining,' but until I see it I reserve judgment.
In Nevada, I'd expect a heavy watering twice a week during the hot days of Summer.
I'm concerned by the volume of soil that isn't drying out in a timely fashion.

Organic fertilizers often require microbes to break the nutrients down into elemental form...
as such, nutrient doses are often unreliable in terms of delivery and known concentrations.
For this reason, a synthetic fertilizer in an appropriate ratio is recommended for use in
container culture. Citrus are heavy feeders, by all accounts, and need the micro nutrients
as well. Most fertilizers - organic or otherwise - do not provide these micro nutrients.

My guess is that the roots aren't colonizing the potting media for some reason,
or that the tree isn't receiving sufficient nutrients from your fertilization regimen.

A better moisture tracking technique is to stick a thin dowel all the way down into
the container. This will show you if the lower layers of soil are actually drying out.
If they're not, then chances are good that there is a saturated layer of soil in which
older roots are rotting or into which new roots will not grow.

Josh

sounds like your soil is retaining too much moisture. i use MG garden soil (70-75%) mixed with perlite (25-30%). i water thoroughly till water drains out the bottom, twice a week in full sun. our climate is also humid. if i'm not mistaken, NV is also very hot, but it is arid. you may want to pull your tree out and check the soil and roots.

Thanks greenman28 and houstontexas123 for your help. I used MG for citrus and palms, while adding one quart extra perlite for extra drainage to the 2 qt. bag of citurs mix. I threw in a one quart cactus mix bag for good measure. Yes the soil is retaiing moisture, as I can tell the top 3 inches dries out but when I stick the meter in 6 inches I go to 5 on the scale. However, nothing has changed in the last 90 days. This AM the leaves were perky after overnight lows of 45 (or 55 or 65...doesn't matter) with the day time highs in the upper 80's once again brought droopy leaves. My other citrus, El Moro and Key Lime are doing fine in the same soil mixture, along with my 8 foot avocado. When I do water, I can see drainage out the bottom of the pot but also see the pott absorbing water, so today I moved the Eureka lemon back in the sun. I am wondering if our persistent dry wind is the culprit? I have added more sand to the soil of the Eureka once but have read that a sandy clay is perfect for a Eureka, no clay in this soil, which would hold even more water.This organic citrus fertilizer is suppose to have soil microbes and I followed directions and only made a tea out of it. If I put it up on the deck railing in full on sunlight to dry it out, it will get full on wind most of the day (live on a hill in updraft area) so I am afraid to stress it that way. Guess I could add more perlite or sand and repot......?????

Avoid the sand entirely!

Well, Miracle Grow soil is notorious for holding way too much moisture.
It is as I suspected.

Perlite won't improve the drainage until the soil is mostly Perlite (90 percent or more).
Otherwise, Perlite's only benefit is that it reduces the overall water volume capacity in the mix.
However, this also reduces the available volume into which roots might grow.

Wind can dry out a plant, but I think the issue here is more fundamental. Wet or saturated
roots cannot draw moisture effectively, so you actually see wilting (drought-response) in a completely
saturated tree. Typically, I'd recommend a shade or screen for the foliage, while allowing the sun
to strike the container. However, all of this will be a mere bandaid until the real issue
is addressed - the soil.

If it were mine, I would re-pot the tree into a smaller container with a proper mix.
Then I would place the re-potted tree in a shady location protected from the wind for 2 weeks.
I can't see how large the tree is, but the container sounds massive for a recovering tree.
Next year (assuming a full recovery), I'd pot the Eureka into the big pot again.

Josh