i have houseplant questions and don't know if they apply here, since it's
not gardening per se, but thought i would give it a shot to see if anyone
can help me.

first question:
i overwatered some plants and ended up with actual mold on the top layer of
soil. white hairy mold. i noticed more dropping yellow leaves on the plant
(diffenbachia) than usual. i scooped out the top layer of soil taking the
visible mold away. i was wondering if the mold is very bad for the plant,
and also if scooping off the top layer and letting the soil dry was enough
to take care of it.

2nd question:
i took cuttings from a citronella plant. they have been in water for at
least 2 (maybe 3 months now). the didnt grwo roots right away, but finally
started to. the stalk from which the roots are growing however seem like
they are rotting. the leaves of the plant look and smell fine. the stalks
are still sturdy, just brown and have a gooeyness on them. can i
successfully plant them? is there a specific way i hsould have rooted and
planted this?