Plant deficiencies and lockouts look the same. If not identical.
I would suggest if you're using a reputable nutrient and correctly following the feed chart, it's unlikely you'll ever experience "deficiency". There should be everything the plant needs already in sufficient amounts.
Which does suggest you're experiencing some lockout.
My own first steps and advice whenever something's wrong is to check environment. See if there's anything I'm missing.
Bottom fed?
Does the pot ever drain and can it?
If you're feeding at 750ppm, where does the excess go?
And how damp is the medium staying? (MJ really hates wet feet!)