Q.Problem with crepe myrtle
We planted 3 five foot crepe myrtles about four months ago. They all leafed as soon as it got warm but all the leaf tips are brown and crisp. We always have either a cold or hot wind blowing. Also, our soil is very alkaline. We live in central Tx. What can I do to make them grow and turn green? We also have six other myrtles that are about eight feet tall that were here before that are doing fine.

Your new plants sound like they are stressed. This article has some suggestions: https://www.gardeningknowhow.com/plant-problems/environmental/what-causes-brown-edges-on-leaves-of-plant.htm
Here is an article about reducing the alkalinity of your soil: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/raise-acid-level-soil.htm