I would do whatever was written on the bottle.
The printed instructions have been thoroughly research before they were printed.
Besides, everyone else who is using these products would be adding the cal/mag first and if this was an issue, there would be a recall or notification through the re-sellers not to add it first.
Also, on another topic, true nutrient "lock out" does not occur until the soil is below 5.5 and above 7.5 pH.
Hope this helps,..........
Organoman.