spooky. they have been a solid consistancy standard for a long time. Must be either a new set of mixing equipment, or something out of calibration for measuring. or they could have switched suppliers of Mag and Calcium compounds of different quality range. time will tell. Once it's on RC it won't go away until all the boo birds are satisfied the problem is identified and fixed. remember Oceanic salt a couple years ago? Ouch!
I believe the old test results of major brands showed all of them at least slightly low on one compound or more. knowing your brand's tendancy let's you make the suppliment when mixing. I recall Randy saying he adds extra mag and calc. to his new IO mix to top it off. but it wasn't that low before.
I still use MEI Crystal sea mix. I know its a little low and just top off with extra calc, alk and Mg to suit my favorite numbers. and still save money.