Thanks for all the advice.

A week or so ago, a white mold started growing from the cork of one of
the flasks. Since then, all the seedlings have been sitting in a
seedling tray with a transparent lid, and seem to be doing ok. The
polyrrhiza has been put on top of a pad of moss, the ascocentrum,
neofinetia and the angrecum are planted in a bark/coconut fibre mix.

Hope they continue to do as well in the future. I guess it is time to
start leaving the lid off.

Geir