I got this fern from a friend who was unable to care for it. It was very dry when I got it, but I've been misting it occasionally, and put it on a little dish with pebbles and water (careful not to let it actually sit IN the water). It perked up for a while, and then this started.

It's most noticeable on that left frond. There are weird transparent white circles on some of the leaves, and the lower portions of the frond are yellow and crispy with brown spots. Is it underwatered? Overwatered? Fungus?

It does have a few little fiddleheads popping up, so it's not in terrible shape yet. But I want to nip this in the bud before it gets worse, especially if it's blight or something.

Thanks!