If anything is out of balance with that particular plants needs, eg;
nutrients
water - too much or too little
too much or too little sunlight
incorrect soil alkalinity or acidity
and an environment that's too harsh for that plant (air may be too hot/dry/cold/humid)
then the plant may struggle to survive.
you say its a fern? Most ferns prefer moist soils, and a humid environment.
Think of where they usually grow - under a forest canopy or in a shaded greenhouse.
Do you have all those conditions correct for your plant?
