Fronds turning completely brown in Haiku. 
The best way to fix ferns that are suffering with brown fronds is to cut back to near the crown to make way for new growth. But before grabbing your shears, it is important to understand what caused the damage in the first place, so that you can solve the problem for good, rather than simply making cosmetic improvements.
Usually, there are 5 reasons that fronds will brown.
- Humidity
- Lack of Water
- Too bright of light
- Over fertilizing
- Transplant shock
I am guessing humidity or lack of water would not be a problem in Haiku. You have said that you have not fertilized and doesn’t sound like you have transplanted these plants. Makes me wonder about the possibility of too much light. Is it possible that something has changed to expose the plants to more light, like a tree being removed, or some heavy pruning? Another thought is the drainage. Is it possible that the drainage is too good and keeping the ferns dry?
Here’s an article about your ferns:
1032-1/8/2022-TF
