Crepe myrtle bonsai

Thank you for your question. If is difficult to diagnose a plant problem without a photo. Misting the plant is not helping it; it just creates a moist environment for fungi. Have you put the plant in sunlight? Have you fertilized it? These plants have meant insect and disease problems, described here: https://hgic.clemson.edu/factsheet/crape-myrtle-diseases-insect-pests/ Without more information, the best I can do is refer you to the following Extension article: https://plants.ces.ncsu.edu/plants/lagerstroemia-indica/ Hope this provides some clues. Good luck!