Q.How Can I Save My Mexican Fan Palm?
I bought a Mexican fan palm at the beginning of the year from an online vendor and it has been growing great since I planted it into its pot. So a couple of months ago I bought another from the same vendor, but it looks like it has been dying. I’ve tried watering less, watering more, and adding plant food. Both trees were planted in the same miracle gro citrus palm potting soil and reside on a patio about 10 feet from each other with similar sun exposure. Are there any other things I can do to get it growing again? The photos are of the first palm I planted that is doing great, and the second one that is struggling.

Certified GKH Gardening Expert
Fan Palms are a desert species that are accustomed to drier regions. This will mean that overwatering can be detrimental to them. This is what I suspect has happened. Make sure soil is well draining and sandy. Water only in mild drought conditions.
Fungicides may help after soil and water conditions are met.
https://www.gardeningknowhow.com/houseplants/fan-palm/growing-mexican-fan-palms.htm
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm