This might sound like a dumb question but it is valid
How do you mix your salt, ie: Salt into empty bucket, then dump water in or Water in a bucket then dump salt in.
Also, how was the water brought up to temp, ie: heater in a bucket for a day or hot boiling water (rushed to temp on stove) and poured into a bucket.
I have noticed through experience, that adding too much salt first into either an empty bucket or smaller amount of water tends to cause calcium to precipitate out. Also, when rushing to heat the water to temp, and adding boiling water to salted cold water, there tends to be precipitate as well.
Just FYI... hope this helps.
Have you tested Alk, Cal, Mag on this batch to see the levels?