Probable cause

Dismantled my vase of forcing bulbs after tracking down an offensive (rotting) odor.  The third bulb with just the barest green sprout showing, but not growing at all, seems to be rotten!  Tried to salvage it by cutting away the bottom, but it appears to go deeper than that.
Took out about half the rocks (so there is not so much water) and put the remaining two back with new water.   Now we wait again and see  . . .