Mites generally cause a loss of the green color initially and then the browning so it is probably not mites. It could be some type of root rot. It is difficult to recommend a control product without seeing the damage and knowing what caused it. Your best bet is to take some leaves showing the damage to your County Extension Office and see if they can identify the cause of the damage. They would then be able to recommend an appropriate, labeled product for you to use.
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