Mold problem with new media after repotting

[ptk]

Hi all. I am a beginner with orchids and originally posted a similar thread in the Potting & Repotting category, but I am hoping to get more traffic here and more help from experienced growers.

Two weeks ago, I purchased Fertilome orchid media, which consists of "Canadian sphagnum peat moss chunks, orchid bark, hardwood charcoal, and lava rock."

I have 3 phals and one of them had already finished blooming and its original media already had mushrooms growing on the bark so it was time to repot (original media was mostly orchid bark). Upon cleaning and inspecting the roots, the roots looked very healthy and plump and stiff. I also sprayed hydrogen peroxide on the roots as a disinfecting precaution read about from other orchid discussions. I repotted the orchid with the new media in a slightly larger clear plastic pot with extra ventilation holes I created on the sides, then watered it since the roots were silvery, dry.

A little over week after that, I had come back from a trip, and noticed through the clear pot that there is white fuzzy mold growth on some part of the roots and those roots turned black/dark gray. My other untouched phals were fine, no mold growth. I was told in my previous thread to continue to water and wait and see, and as of today (another week later), I'm seeing more dying roots and more visible mold inside the media. And another surprise is that recently, I also notice possible mold growth on the surface of the same exact media that is holding my bromeliad pup. I planted the pup in the same media 3 days after I repotted my phal. The growth looks like speckled, powdery white growth and its very visible on the black charcoal chunks and lava rock, and I also see this growth within the pot of my phal.

What should I do step by step now to save my first orchid?

Note: Not sure if it matters, but the new bag of media does contain a lot of charcoal/rock dust. Was I supposed to rinse the media with any solution or plain water first?