I currently use Red Sea blue bucket. I haven’t tested alk or anything like that yet.What salt are you using by chance? Not all salts require a 24 hour mixing time. It's unrelated, but a good lesson in not everything being what we think it is. I use coral pro salt in several of my tanks which actually requires a maximum mixing time of 4 hours. Also use red sea blue bucket, which is essentially indefinite. I don't think it could be the cause of the issue, but high alk salts could also impact pH, which could cause stress to your fish. I don't think (I want to reiterate that) it's the issue, but a possibility. High alk salts would be anything over 10 dkH in my book, coral pro, reef crystals, etc.