not saying at all the cal-mag isn't in the soil
I'm saying you might be overwatering, which is causing the plants pH to swing low/high and lock out calcium or magnesium
the solution wouldn't be watering more, the solution would be to maybe add more lime next time, mixed into the soil, and on top ( 1 tbsp/gal mixed in and a month after planting do an extra tbsp sprinkled on top or something)
what actually happens is the overwatering causes slow release nutrients to break down too fast. The increased salinity will thus drop the pH and cause lockout.
A solution might be flushing, until water comes out same pH. From there you now add nutrients to the water and pH it before adding to the soil
to avoid this from happening, maybe mix more/less perlite in with the soil. If the soil is too dense the slow release nutes will break down really fast because it is way too wet when you water
if the soil is too light, there won't be enough soil although I would rather my soil too light than too heavy.
curious how to find out how dense your soil is? just take it and rub it between your index and thumb, you will notice the difference between good and bad soil. Good soil will make things super easy
but no matter what, over watering will cause issues that tend to make you go out and add stuff that doesnt help