Your temps are fine. That wasn't the issue. Sounds more like just a freak occurrence than anything else. Unfortunately these things happen. Some of them just never make it for whatever reason - it's just part of breeding.
From what I've seen and read from your other posts, your husbandry sounds like its just fine, so as far as I can tell, you are not to blame for this. So don't beat yourself up or start to needless worry about your other guys.