I apologize for this delayed reply to your gardening question and hope it is still helpful to you.
I'm not sure what is wrong with your fountain grass. If it is the edges of individual grass blades that are browning this is usually a sign of a lack of water or in some cases excessive fertilization with a salt-based fertilizer. If it is the clumps themselves that are dying around the edges then I would again consider a lack of water as the likely culprit.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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