There is a spot on the ceiling under our bathroom. Maybe about 3 years ago my husband put tile in the bathroom. Could the water be coming from the edge of the tub that should be sealed, because I never thought that my husband sealed it correctly. Or is there a possibililty that it is coming from somewhere else. The spot is not dripping or anything, it just looks damp.

A small leak under a bath could be many things. It is likely that a pipe or valve would continue to leak so the spot would be big and active. If you have just a small spot that has now dried up it may be what you suspect. The ceiling is already damaged and needs repair so pour some water in the area you suspect is not sealed properly. If the old spot comes alive you have it.