Onc and Phal: White stuff on potting mix and brown roots?

[Summerlove]

Hi there! I am a newbie on this forum, and a newbie with orchids!
I managed to finally kept some alive through their blooming phase and now the blooms are gone and they are growing some new leaves. I have't done anything different, other than moving them to a new location (similar amount of light, but possibly a little less airy - on shelves rather than open space.)
Lately I noticed that the oncidium potting mix (at the surface) seems to be moldy, and the roots are also turning brown. (Image attached)
For the phal (it has a clear pot), parts of the root near the bottom of the pot, along with the nearby potting mix seem to have fuzzy white coating too.

Is this snow mold? And what should I do to get rid of the mold?
Also are the brown roots in the (oncidium) picture a concern?

Thank you!!