My observations have not been very scientific - I combined a couple of experiences that could have been coincidental with anecdotes that I read online, including here. One thought, though, if you are using a weak dilution of the MG (something like 1/2 or 1/4 of recommended for containers), that could explain why you don't have a problem with it. I tend to mix my ferts full strength (because I have so few trees in refinement).
I use the same brand! Good stuff. As long as you are not keeping the soil soggy, I don't imagine continuing to use that will hurt anything.