Answer: It sounds as though the planting site has become too wet for your yucca. Typically the leaves lay flat when the roots are distressed. It won't hurt your plant to dig it up and transplant it to a higher, drier site. The leaves are damaged anyway, so they'll eventually dry up and you can cut them off. Even if you only dig it up to check the root system and the drainage, you can replant in the same spot if everything looks okay.
Best wishes with your plant!
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