Help, Mold!

[Ocelaris]

My Vandas are doing wonderfully air rooted but my oncidium genera, cattleya are molding at the crown, just 3 days into their new home and even though I cleaned off the organic material, they are wayyy too moist. I have lowered the humidity in their growth space ~60% during the day, less at night, and am venting fully at all times...

Does no one else have this problem? It's especially bad with the phrags, starting crown rot, even though leaf growth is decent. Should I just cut side holes in the pot to let more air in? I don't water but every 4-5 days or when no water is in the reservoir.

This is an ongoing problem, the roots of the phrags are very bad looking, no new root growth to speak of. I have one LC which is doing incredible (ok it's insane), but none of the others seem to be enjoying their semi-hydro in the same manner...

Should I clean up with Thiomyl or Physan? Air movement is pretty decent given my small area... the pots are tall and narrow though, well, relatively, they're Rays' 4.5" pots, which are maybe 7" tall? Relatively tall/narrow compared to the 5.5" which are the same height but 3" wider...

Thanks, Bill