Can anyone identify this problem and hopefully tell me what to do, please?

looks like too much sun. it should drop after being completely burnt off. new leaves coming out should tolerate sun better. or if you wish, keep it in the shade and move it to partial sun when ready. 

The picture is of a leaf that did come out in the sun. The problem started on one tree and has moved to others. All the effected leaves came out in full sun though.

Tami, what does the top side of the leaf look like?

That's the puzzling part, the top looks normal.

I used the computer zoom and it does not look like leaf burn to me. I can also see it on the smaller leaves
but can not tell if they are from the other plant in the back ground. I don't "think" it is rust either. I know none
of that helps but it is unusual to me.

It could be a symptom of over or under watering.  I see it is 77 degrees there now. Has it already been real hot/humid?

Yes, we have had some pretty hot and humid days and then we get a cold spell for a couple of days and it might get to 45 at night. I am heartily sick of this weather and it can feel free to stop now!
Sorry for the rant...blush.

Tami,

Can you post a couple of more pics please?  My first crazy thought was that it looks like it was burned by heat such as a BBQ, but you say it is on other leaves and only the top side so that can't be it.  More pics might help with the ID.

I do not think it is organic, it almost looks like a chemical overspray, but it has not effected the stem structure. it really does not make sense to me.

Steve, It's only on the underside of the leaves and the top side looks fine. I will get more pics in the am it's a little too dark now. I am baffled though but very concerned as it is starting to go to more than one tree.

Shooting out of left field here, do you think it might be because the pots are on concrete or perhaps they don't like full Texas sun? I was concerned about that as well and started a full sun thread.

Anyway, I will post more pics in the morning and thank you all for helping me.

It looks like some type of micronutrient deficiency to me, how have you been fertilizing?

It looks like the sun's rays are striking the brown part of the leaf more directly and closer to a 90 degree angle (straight on to the leaf).  The closer to straight on the more damage will be done.  Chemical overspray is always possible but I would have expected to see the adjacent leaf surface to the left affected more.

I have ordered tons of Mykos and Azos and will use both liberally, I will fertilize tomorrow and see if that helps. 

Suns rays? On the bottom of the leaf? Got me thinking....could the sun be shining back off one of the cars and hitting them? All the damage is on the right side of each tree! I am moving them to the back yard tomorrow away from concrete and vehicles. I also went ape sh@$ with sevin powder this afternoon and believe it or not they are uncurling.

Mykos, Azos, superthrive, Miraclegro, (not to mention they are in compost with worm castings) Sevin powder, a big move. Jeez, I am way too emotionally invested in these things.

The leaves are curled up.   Is the right side facing south or west?

North

Then not sun!  :)

But the truck is parked North yet and I am wondering if the reflection off the bumper maybe?

What else is in the mix besides compost and worm castings?

You should not have any deficiency then... I am not sure MG has micronutrients but compost does. Too much is a bad thing too though, and if the mix stays wet that will cause problems also.

Lots of pine bark.

It may be too much water...look at this thread...it seems like the same issue:

http://forums.gardenweb.com/forums/load/fig/msg041148481294.html

OK, they might need fertilizer then, pine bark does not hold nutrients well and needs more frequent fertilizing compared to other mixes. Has it rained much lately? That really leach fertilizer.

And what about lime? 

I have lime to put in and I will fertilize tomorrow. I am kind of going with Tim as he had the same problem and was sure it wasn't too much water. It showed up several days ago after the tree had had no water for 3 days. I have a fantastic drainage in the pot so if I didn't water and God didn't water it couldn't be the problem.

How much lime do you use?

OMG by the time we're done we won't know which action fixed it, assuming it gets fixed.

Tim said in the other thread that it just eventually went away :/

These trees can drive a person nuts. I should have taken some botany classes first.

I mix in a handful per ~5 gallons of pine bark. It is probably better for you to use half that and add it on top once a month for a few months, when it is not mixed in less should be used more frequently.

Okay, I'm going to guess 2 handfuls for me the in each big pot. We'll try that too, I'm gonna have completely stoned trees. LOL