I know nothing about this but from
this, which I presume you have already seen, it does appear so.
This why I prefer hydro, even though I see fantastic results from others in soil. It looks like mag, but then I wonder, or is it lockout, what if I put more salts in and it wasn't and on and on. I'm already having enough trouble trying to decide exactly when and where to defoliate. At least with hydro, I know there are no salt build ups and I can directly inspect the roots and even if there is a nutrient imbalance that will be corrected at the next change. I'm just giving my reasoning, I'm not telling you what you should do, I'm just sharing my thoughts.