Students become unresponsive after I gave them 'low' marks

The students received their report cards last Friday. During class today, I noticed students in the top section were unusually quiet and disinterested in the discussion, with some even sneaking doing other tasks for other subjects. I heard some of them saying to other teachers how I gave them low marks compared to their other subjects and wonder if I'm that type of teacher. But I believe I gave them fair grades according to what outputs they submitted.