Nah, just one of them stressed out the other to the point where the other one wasn't digesting his food properly. So he starved...
The breeder in question said it was normal for them to get MBD randomly and go away by themselves like with his Crested, and he house them together and apparently "never had a problem." I am willing to bet his co-housing caused his Crested Geckos to get MBD from time to time.
It was my fault for even listening to him. Now I know what some varanid breeders mean by "Just because they are reproducing, doesn't means they are recieving what they need."