1 on your number pad is telling warlock 1
/petattack

2 on your number pad is telling warlock 2
/assist warlock1
/petattack

you just change your targets with the lock

idont know if theres any one button that tells both pets to attack somthing different, maybe if they were tanking then it could have somthing to do with the targets target. your probably better off getting some info from one of the pros about this.