, keep in mind that just because you are doing things right, the damage was already done. Heck, that damage probably started in the store where you purchased the plant. Generally speaking, our big-box store and grocery store employees don't have a clue how to care for these tropical plants. Our Lowe's is "famous" for under-watering or over-watering their tropical plants. The thin, tender fronds that were damaged, probably from dehydration but possible from another cause, don't simply recover to their normal, healthy state. New growth is where you want to see healthy fronds. Your plant may well lose many if not most of those older fronds. Don't fret about that. It won't be pretty but that's just Mother Nature's way of saving the plant by sacrificing the weak, damaged fronds.
I did not notice whether you are misting/spraying those fronds every day or two, but that will help raise the humidity as well as allow the new fronds to stay hydrated.
Keep working at this. I have confidence you'll get these plants through this rough time.