Cross-character achievements

I don't know if I'm posting this in the right place, so forgive me if I made that mistake. I'm confused with some achievements transferring to other characters on the same account. I have Exalted with Lorewalkers on my Pandaren Monk in Horde, I got it by collecting scrolls and getting achievements and quests in mail and everything in order. Now the problem appears. I also have a Dranenei Hunter in Alliance, I have achievements for her as well, and because of that I get nothing from scrolls anymore, so I can't get reputation with Lorewalkers. Is there any way of getting multiple Lorewalkers Exalted reps or am I just stuck like this?