Never had one, but it's a nice looking plant.
Looks like yours was fine and healthy for a while, at least 7 funky leaves now but new growth seems better.
I assume that gorgeous pot has drainage and love the humidity tray but would still guess a humidity drop a while ago could cause that.
Did anything change for it about 4-6 weeks ago that could've lowered the humidity? Crank the heat in cold weather, location change, more light/heat as spring kicked in? Skip a couple waterings?
Whatever you're doing now seems to be working.
That said, what are you doing, in regards to watering?
Give it some time. The new growth looks great.
To play it safe you could give it a much larger humidity tray and deeper pebble depth.
I see debates over whether pebble trays are effective. Personally I love them and figure they can't hurt.
You can always liven up the gravel on larger trays with cuttings, pretty candles (while not lit of course), crystals, neat pieces of wood, kid's action figures, etc. I saw a great one a while ago with a bunch of local handmade glass marbles. Amazing.
Local article on them:
https://www.northcoastjournal....