Use the condition, not translation guesswork, to read كُلٌّ.
Construction Mudaf-ilayh Meaning
كُلُّ مُسْلِمٍ singular indefinite every Muslim
كُلُّ شَيْءٍ singular indefinite everything
كُلُّ الْمُسْلِمِ singular definite the Muslim as a whole
كُلُّ الْكِتَابِ singular definite the whole book
كُلُّ الطُّلَّابِ plural definite all the students