I seriously doubt the nose bleed has a direct relation to your harmala consumption, but im no doctor.
Im attaching to this post the publications I found on harmala poisoning (all with syrian rue). Notice that the dosages they take are way way way way higher than what you took. Those people took 50-150g syrian rue!! thats the equivalent of a few grams (!!!) of harmala alkaloids plus the fact that syrian rue has some other potentially more toxic alkaloids, such as vasicine and vasicinone!. Also notice none of them talks about nose bleed, but one of the cases does mention some vomiting blood.
I think you have nothing to worry with those 500mg harmalas in a 7 hour period. People consume several doses of ayahuasca in long ceremonies, probably amounting to similar or even higher amounts of harmalas than what you described, and I've never personally seen or heard of such problems. Do tell us if that happens again though, its always interesting to know about these things.