Beginner Gardening: stimulating growth on mounted staghorn fern, 1 by mariakc

mariakc wrote:
Hi all,
New to the forum here. For my birthday this year (oct.), my boyfriend bought me a great mounted staghorn fern. It's currently hanging off the side of a South facing window, so it receives indirect, bright, but not sunny light. I have other plants growing VERY well right in front of this window (e.g. african violet, chinese evergreen) so I know it's not too shady. It's near a vent. I mist all my plants at least once per day, and I usually water the staghorn with filtered room temperature water every 2 weeks or so--usually only when it wilts a bit.

All this being said, I'm worried about it. It got a new little sterile frond about a month after we got it, but now this is turning brown. There hasn't been any other new growth besides this.
Is this bad? I know that it's winter, so maybe in Spring it'll perk up. I've just heard people talk about how crazy their fern grow, so I hope I'm not slowly killing mine.

I've attached a picture. Some caveats: it's drooping because I just watered it today. The white stuff is diatomaceous earth because I saw some ants around the plant. Also, I'd watered it about a couple days ago and it didn't perk--I think the ants maybe have something to do with that...
Any advice is appreciated!! Thank you!!
-maria