any more details? Old growth okay, no browning or spotting? New growth browning; is it the tips, margins, midrib out, softened water (NaCl or KCl), recent fertilization or amendment, etc? Is it getting too much direct sun? Inside/outside pot/ground?

They're called cast iron because they are tough buggers so first look to any aggressive changes that the tender new growth can't tolerate like the hardened old growth. If nothing much has changed and you feel it may be getting too much water, certainly decrease the watering amount and monitor the new growth. If it's getting direct sun, try shading it for a while. Hard to say much more without more details.

thanks, sorry, I guess you would need more info. These are all in the ground. they have like 15 plants, pretty much in the shade and all plants have this. the old growth looks ok. the new growth is all brown. adding picture.

If they're newly planted it's probably transplant shock and they'll outgrow it.

They are definitely tough plants and survive just about anything, but they do develop ugly foliage if they are stressed by too much sun, not enought moisture, or too much wind (shredding the leaves). They are an evergreen plant, so they do not shed off dead/dying foliage and I find that, regardless of the cause, it is necessary to remove brown/dying foliage and allow new leaves to grow.
Molly

They are definitely tough plants and survive just about anything, but they do develop ugly foliage if they are stressed by too much sun, not enought moisture, or too much wind (shredding the leaves). They are an evergreen plant, so they do not shed off dead/dying foliage and I find that, regardless of the cause, it is necessary to remove brown/dying foliage and allow new leaves to grow.
Molly