Update on this guy too. All I did was up my water changes to twice a week and his eye has cleared up. It doesn't look quite the same as the other one, and I'm not sure if he can see out of it, but he is perfectly fine now. His eye has no cloudiness or whiteness left at all.
I don't know if it was caused by injury or just that this species needs extra clean water. I spoke to a fellow hobbyist who had five or six of these guys, and it took the death of all but one to realize that they need very clean water. So, water changes twice a week now.