Welcome to NGA,
@Tesy. Please take a moment to go to your "Profile" and enter your location, including your USDA zone. It helps to know this when answering or asking questions.
In my experience, your plant is drying out far too much and for far too long. Young plants need much more frequent watering than those that are mature. Your plant is less than 1 yr. old, and that's a really young plant. I would begin to deeply water (soak the plant in a tub, basin, or bucket for 30-60 min.) every 3-4 days and then, once you see all those fronds perk up, you can do this weekly. Simply misting/spraying your stag just won't cut it. Believe it or not, a skylight may afford very little (bright) light to your staghorn. It all depends on the type of skylight, its orientation to the sun, and how much sun actually strikes it and for what amount of time (tree shading, for example).
Lack of sufficient bright light won't kill your stag but it will result in far slower growth. Deal with the water issue first and foremost, and then decide whether your light is sufficient. Fertilizer is needed for best growth, but for now, no fertilizer. Begin that in the spring, 1/2 dose of balanced fertilizer every other month will give you good results.
