Cannas can tend to cycle in bloom. I can't identify the bugs you have based on the description. I suggest you take a sample of the leaves and the insects to your County Extension Office for identification, and for appropriate control recommendations. They have a horticulturist and Master Gardeners in the office and someone should be able to identify the problem with a sample in hand. Their contact info is:
Texas Cooperative Extension in Tarrant County
401 East Eighth Street
Fort Worth, TX 76102-5504
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