Good afternoon,
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Most pond plants will die back completely for the winter, losing their leaves and stems. The only exceptions to this are one or two evergreen marginals such as Corkscrew Rush, and some oxygenators such as Spiked Water Milfoil. Some die back earlier in the year immediately after flowering, but most keep their leaves until the first hard frosts.
I would advise re-potting the plants now that the Spring weather is here and you should see them come back to life.
Best wishes,
Laurie