I apologize for this delayed reply to your gardening question and hope it is still helpful to you.
Agave is VERY tough and if one is dying it is either due to continued soggy wet soil conditions (poor drainage and overwatering) or to the agave weevil, an insect that tunnels in the base, essentially severing the top from the roots. There are pesticides that will kill the weevils but using them is generally not effective since once the weevils are in the plants no pesticide can reach where they are living. If the plant dies look at the base for signs of interior tunneling. Your County Extension Office 512-854-9600 can help with diagnosis and control options.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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