Sorry to hear about that.
I had the same problem, and I decided to wait a couple weeks and my male didn't make it either (I put him to sleep last night). My water parameters were all fine, so I am starting to agree with those that say GBRs die really easily.
I had no aggression issues from the male, I don't think it will be a problem.
I will probably get a pair of Bolivians, once I know it isn't my tank.