Green or white fuz spots on the
surface of the log:  This is a green
mold which usually forms on the log
in a commercial growing
environment.  If you see this scrape
it off and spray a very light mixture
of bleach/water all over the log.  
Green mold forms because of too
much humidity, so you may want to
cut back on the watering a little
and take the log out of the tent.
The white stuff you see are
spores dropping from the
Tanins in the soaking water
from the sawdust in the logs.