[Van down by the river]

I think you just got a rare bad bucket.
My sympathies to you.
I've mixed many thousands of gallons over the last 13 years. I've never had any problems.

I've used KENT and IO...if I remember correctly, they are quite comparable and may even be manufactured at the same facilities.

For all the people that say Kent is better than IO, I doubt that there is much difference.
Are they made at the same factory? Yes, this is true, Kent is manufactured by IO. per personal communication from various IO reps.

The salt is processed with all the same major elements. Kent supplies the minor trace elements to IO for final mixing. The idea is that there can be no conflict of interest in salt recipes on behalf of IO, if they don't know the exact final mix Kent uses. So they may even be the same.