I’d bet it’s missing sunlight, those things thrive in direct sun.
Second guess is that it’s overwatered… does that pot drain well the water? it should definitely not be sitting in water and I would not water it very often.
It can be a mix of both things
I am living in a dry region (now it’s like 60% bc it’s winter, but in summer reaches almost 0%humidity). I was like you and also got humidifiers before, but my recommendation is that you forget about it and just let nature do it’s thing and plants adapt to your environment.
Obviously we cannot have ferns, but some plants like hoyas and such, you may be surprised that they adapt at the end and even thrive. At the end you do as you think best, but overcaring for plants that may be sick or cannot live in your climate is too big of a challenge long-term, take that into account