Is this a form of discrimination ?

my daughter works in a nursing home as a cleaner. all of the cleaners have been told that they must not talk at all to anyone, this means nursing staff, residents, themselves, any visitors etc. this is on threat of a written warning ..... two written warnings & they face the sack. this means they must spend the whole working day (barring any breaks) in silence. none of the other sections of staff have this imposed on them, just the cleaners. is this discrimination against a workgroup ?