Sounds like you have Texas weather and gardening figured out pretty good! In order to help more specifically I'd need to know which vegetable you are referring to. Tomatoes don't set well in this heat unless they are the small fruited cherry or grape types. Even peppers tend to abort in the summer but will set very well in fall so keep those plants going for now. Squash and cucumbers are also not good at summer fruiting.
I am concerned about the 2-3 hours of direct sun. That is inadequate to support fruiting and root producing veggies. You might want to increase the size of your planting containers to make it easier to keep the soil adequately moist. Find a way to shade the pots from the sun as the extra hours may be heating up the container making the roots too hot. With some shading I bet you could go up to 6 hours of sun just fine if the particular vegetables are summer tolerant to begin with.
Thanks for the question. Please stop in again soon!
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