Bell County Texas
It is unlikely that chinch bugs or white grubs are the cause of the shrub damage. It is possible that it may be some type of fungus causing the decline. I would recommend taking photos and sending them to your area Extension Office (they should have Master Gardeners that can help you) or maybe collecting samples and taking them into the office.
Thank you for your response. Maybe I have been watering them too much and thereby causing the fungus to grow more. I will investigate the problem with the local office.