I have noticed occasionally that Priests and Deacons do not add water to the communicants cup. Is this optional? They always add water to the Priest,s chalise. It always makes me feel that the communicants cup is incomplete or not valid.
The General Instruction of the Roman Missal is silent on the matter. It only mentions adding water to a chalice, it never mentions a plural. Water being added to the wine is also not essential to the validity of the sacrament.
Therefore it would seem that, as of now, it is perfectly acceptable to either add water to every chalice or the main chalice alone.