I have been using the tablet form of Natrol Melatonin for over 2 years
now and have never had a problem.  On the bottle it says:
 
calcium 28 mg   3% (as dicalcium phosphate)
Phosphorus  20 mg  (as dicalcium phosphate)
Melatonin  1 mg
Other ingredients: Cellulose, Stearic Acid, Cellulose Gum, Silica, and
Magnesium Stearate.
 
This is the information on the bottle.  I know there is a liquid form but
it has alcohol in it and I don't use it.  I have 6 kids on it now with no
ill effects.  I wonder what the difference is.  Curious.  I hope all is
well with the rest of your kids.  It is horrible to loose any of them no
matter the cause.
 
Terry and 15 Frolicking Fur Children
[Posted in FML issue 4360]