Are are all or some turning yellow and falling off? Trees will normally get rid of the older leaves. I suspect that is what is happening and not damage due to over watering.

Not all of them but it seems like quite a lot considering how many my small tree had to begin with. It looks like a lot of the lower ones are falling off, so you could be right.

What is the soil and how often do you water? Do you add enough water so that it drains out of the bottom of the pot? What is the average day time temperature? Did the leaves cup (outside edges curl up)?

From the photo it seems the new growth is yellowish; and new growth is what tells you about the current state of the tree; older leaves tell you how it WAS.

The soil is a mixture of miracle grow citrus, sand and perlite.

No I have not been adding enough to make it drain. Perhaps that is the issue?

Average daytime temperature has been pretty hot 80-90 degrees. Also very humid.

The leaves that are still greener don't really cup but they have a wave around the edges. Ypu can kind of see the wave in my photo above. Once they turn yellow they completely flatten out.

Vladimir, a few of the leaves of my big trees cup up like that (the newer ones)...it's a more recent phenomenon. Why does that happen?

Janette: You have been having hot temp, leaves are wavy, and water has not drained out of the pot so you may be under watering, It is hard to tell. This is how to tell if the tree needs watering: take a 1/4 inch dowel sharped to a point or a shish kabob stick and stick into the soil all the way to the bottom. Wait about 5 seconds and pull it out. If there are soil particles sticking to it or if it feels cool and damp then it does not need water. It is important to let water drain from the bottom, to prevent buildup of salts.

Laura: Some of my trees do that, too but the leaves are not yellow ,they are not dropping leaves and they seem to be OK. I don't know why they do that. I admit it does worry me sometimes. It's like taking care of kids, isn't it? Like when they get a fever and you worry.

Is your tree is FULL hot sun when in the 90's? Were they ever green and if so, when did they start turning yellow?

First I would like to know if it's possible your roots are over heating...........That;s a priority... What zone are you in?

Nanette, good luck with your trees! Vladimir, thank you. Yes, it's like with kids...I've had one kid with a fever and the leaf curling on my Persian all at once! I'm a bit frazzled! ;-)

Give your tree episom salt to help it obsorb notation from the soil and a micro nutrient mix like azomite and your problem will go away

Janette, I am not clear as to which leaves are falling off. If it is the older leaves toward the bottom of the tree, then that is normal. However, the new growth does not look normal. Johnmerr is correct: new growth tells you what is going on now. You may be under or over watering.

Glenn Jones seems to think that your tree is suffering from some sort of nutrient deficiency but I see NO evidence of that. DO NOT GIVE your tree epsom salts and azomite because that may very well kill your tree.

I think I may have been under watering. I have started giving it a little more water, hopefully this will be the solution. Thank you all for the help. I will give an update in a few days if I see any changes!