I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
That is difficult to say without examining the plant itself. It may be due to physical damage from working around the plants or bright sunlight burning the foliage, or pest damage from scale insects that sucked the juices from the plants. I suggest you check the soil moisture and see if it is dry or possibly if it has been staying soggy wet. Both can cause loss of roots and the subsequent yellowing and browning of the fronds.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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