Both of them hit their opponent while they were down

But only one of them got DQ'ed. :20 seconds Corley was clearly down. First punch was okay, 2nd punch was uncalled for(Didn't get a point deducted or anything) :28seconds Roy gets DQ'ed Jones' punches were clearly more obvious than Cotto's, but why is their exceptions? If you DQ one fighter for hitting another fight while down then shouldn't all fighters that hit their opponent while down be deducted 1 point or 2, or DQ'ed?