Sounds to me like you may have overwatered your tree. In the future, use a tooth pick or a chopstick and emerse it in the soil. If the wood comes out with soil sticking to it, don't water the tree. Also, it is good to mist the tree, especially where it is hot.
Though, I think it is time to put this tree in the compost and try again.
Also, a nice organic fertilizer like liquid seaweed will keep future trees nice an healthy.
Try researching what trees will grow best in your climate and buy a tree that will suit the heat of texas. Trees will be much healthier if they are grown outside.