I have several crape myrlte trees which were planted in late March.

They have been doing great, putting on much growth for young plants and blooming
with colors as expected all summer.

Now, in mid-August, several have some yellow leaves. One has quite a few and
almost no colored blooms left.

What is likely to cause these yellowing leaves? I did a search and found no
mention of yellow leaves on crape myrtles aside from the change of color in the
fall.

There have been a number of ants running up and down the branches. When I
checked the trees after seeing the yellow leaves, there seem to be more than
usual. I'm not sure if this is the cause. I also don't know what kind of ants
they might be; they seem somewhat small for fire ants.

I've ensured the trees have a lot of water several times a week. There still is
time-release fertilizer on the ground from my last application a couple months
ago. The soil is mostly sandy and I live in Orlando, FL. The trees get full
sun much of the day. It's been in the lower-mid 90s and high humidity for at
least 2 months.

Do I need even MORE water? Do I need some added fertlizer? If so, what kind?
Do I need to cut back on the water? Do I need to kill the ants? If so, how?

Any information on yellowing of crape myrtles in August in FL would be useful.