It's not recommended to put food scraps that are not composted in with living plant material. You don't want to invite decomposers (microbes and insects) that break down plant material to the same space where living roots are trying to grow, so remove those banana peels.

Here are some general recommendations as far as care of your staghorn fern goes:

Watering. Water regularly with room temperature rainwater (or distilled water, as you are doing), either by pouring it onto the moss or immersing the root ball in water. Allow the growing medium to dry out between waterings, as staghorn ferns can rot if overwatered. Water more frequently in the summer and less in the winter. You may be watering too frequently and this could be causing some rot issues now that we're moving into winter.

Light. Place in bright, indirect light. Staghorn ferns can tolerate more direct sunlight when temperatures and humidity are high.

Temperature. Keep in warm temperatures above 55ºF. Staghorn ferns can survive brief freezing temperatures, but it's best to move them indoors before nighttime temperatures drop into the 40ºFs.

Humidity. Provide high humidity levels. You can mist the shield leaves weekly or place the fern in a humid room like a bathroom, like you are. I don't think too much humidity is the problem, rather it's likely that the root ball is overwatered and needs to dry out some.

Fertilizing. Fertilize every two to four weeks with a standard liquid fertilizer. You can also use a 1:1:1 ratio fertilizer. Young plants should be fertilized monthly during warm months and every other month during cooler months. Mature plants can be fertilized once or twice a year. You have a mature plant there, so if the plant recovers you could give it a low dose of fertilizer in the spring.

Pruning. Don't prune the fern, and leave the brown shield leaves on the plant. The shield leaves are important for the plant's health. If some of those foliar fronds die back and can be pulled out without much strength you may remove them, but don't cut them off.

Pests and diseases. Monitor for spider mites, aphids, mealybugs and scale. Black spot can occur if humidity is too high.

Further Reading:

https://hort.extension.wisc.edu/articles/staghorn-fern-platycerium-bifurcatum/

https://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/staghorn-fern/#:~:text=A%20good%20rule%20of%20thumb,sure%20to%20follow%20label%20instructions.

https://plants.ces.ncsu.edu/plants/platycerium-bifurcatum/