How long ago was it when you transplanted the starts to the bigger pot? If you put it into full sun in 90 degree heat right after transplanting, it could be transplant shock. When I put my new starts into their permanent pots, I keep them well watered and in dappled shade with protection from the wind for a few days. It takes a few days for their roots to begin doing their job and become efficient at taking in water. I use a fast draining mix (5-1-1) and don't worry about watering too much when I first plant my starts, especially if the temperature is high.

I love angelonia. Even though I have a very different climate than you, we had a heat wave and drought last summer, and my angelonia thrived.

Hi I am in the Round Rock area, north of Austin, and I planted some too about 4 weeks ago in a pot- and while it is in full sun, it has late afternoon shade, and I had similar issues as you stated for the first 2-3 weeks after I planted it.. It has since stabilized and is thriving. With the current temps, I have found that even my most drought tolerant/ low water needs plants ALL needed daily watering and less intense sun for the first week to 10 days after transplanting into new pots! I love the angelonia, and was very concerned about mine for the first week, but she pulled through fine!