That is either a fungus or a bacterial infection. These generally don't cause major problems for the plant although they are unsightly. There are sprays you can use to prevent the problem if you time the spraying and choose the proper product. I suggest you contact your County Extension Office and take in some leaves if you still have them on hand for them to examine and prescribe the best course of action for your area. Their phone number is (904) 284-6355 and they are located in Green Cove Springs.
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