Could likely be a fungal disease. There's nothing you can do; your tree fern will either survive or it won't.

It would be somewhat helpful to those trying to help you to tell us where you live.

Thanks for the reply. I live in central Florida currently. Would treating with a fungicide be beneficial?

Maybe the soil is too heavy,too peaty. They like water to run through the rootball. It might be suffocating.

It's possible the old store mix it was in was but I have it in a mixture of pine bark fines and perlite so it seems like it'd be well draining enough. Maybe it's still suffering from its treatment at the store?

Could be underwatered. The first to die are the newest leaves. Put a saucer under it if you cant' water it as often as it needs.

Do you know the genus and species? I grew Cyathea cooperi one summer and I could NOT ever let it go dry or all the fronds would collapse.