Hi
I'm a bit late to respond here, but I think since you cannot put the scheduler-map on the IRB interface or it's units, you need to put it on more phyiscal interfaces. Same as you already did for one:
set class-of-service interfaces et-0/0/50 scheduler-map MY-SCHED-MAP set class-of-service interfaces et-0/0/50 unit * classifiers dscp MY-DSCP