Back in my younger days, I always had a Naso, and they lived for a long time with no issues.
A few years ago I thought I'd get a pair. When snorkeling in Hawaii I noticed I always saw them swimming in pairs. So I got two, a male and a female, but blonde. They didn't last long. I got another pair. Also didn't last long (a few months generally). I got another, single this time. It disappeared. Got another pair. One died. The remaining one seemed to do well. Then I discovered (6 months later) that there was a Naso in my overflow. I rescued it and put it in the tank. This was the one that had disappeared 6 months previously. Now I had two healthy adjusted Nasos , but they were both male. No matter - I was happy to have them and they got along well. They lived about 2 more years then died for some unknown reason.
I have also suspected that cyanide is the reason for their short lives.