As you can see from this thread and literally dozens like it on MR alone, there is no consensus or anything close to it regarding which salt to use. The same goes for all the serious attempts at testing salt mixes--- every single test comes to a different conclusion. The truth is that none of them come particularly close to natural sea water and nearly all of them are "good enough" to use. Find one that seems to agree with your system and stick with it-- changing salt mixes regularly IMO causes more issues in and of itself.
I have used IO for over a decade without issue and would continue to do so if not for being asked to beta test the new ESV salt. Having done so, I think it is an improvement based on ease of mixing and what I know, because I know the manufacturer personally, is the use of super high quality ingredients. That is what I'm sticking with from now on.