Watt ferns are sick

[Tropicdoc]

What’s wrong with these wart ferns?

I’m guessing fungus because I sprayed some antifungal and the black spots partially turned white. But, how do I stop the spread of this disease?

[NOT A TA]

I though someone with more long term experience with wart ferns in particular would have chimed in by now but since no one has.....

I'd cut them to the ground and put all the leaves as well as all the litter and any other loose organic matter on the ground in a garbage bag which you will put in the trash. Clean entire area to the soil, including any organic mulch, use a big shop vac if necessary.  Gravel/stones can be left in place. Then put down some new mulch.  Do not use the leaves, old mulch, or old litter for recycling/compost, just seal it in a plastic bag(s) and get rid of all of it. Once the area is cleaned, if you need to water as the new sprouts come up do it in the mornings so the foliage will dry out not late in the day.