Phalaenopsis stem rot?

[IvyElle]

Hey, everyone! My phal is giving me some trouble.

I'm new to orchids, so.. *sigh* here's a long story. When I first got this phal, I repotted it into bark from sphagnum moss. After her leaves wilted and her flowers all dropped, I assumed it was because I had failed to increase watering frequency, which I fixed right away. I now water her once every three or four days. However, I'm starting to suspect the wilted leaves are also due to this... interesting looking stem/root issue.

I'm kind of confused- the crown is healthy, but the stem is black. The areas where the few healthy roots meet the stem are, as well. The roots themselves look quite rotted, and the root rips are mostly dried and dead looking. I'm hoping I'm not too late to fix it because she's been in my care since November, and I'm assuming this rot has been with me since then, too. I feel awful about this phal abuse.

I've heard a lot about hydrogen peroxide, but I'm hoping to get any advice before going through with that treatment. Thanks, everyone <3