Once degraded, leaf integrity usually doesn't improve. (old leaves are old news)

Big Bloom is a catalyst tea formulated to compliment the Grow Big and the Tiger Bloom.

I've been using unsulfered molasses instead of CalMag Plus for a while now. Molasses has all the calcium, magnesium, iron and carbs you'll need. 1 teaspoon per gallon, once a week. Molasses does act like a 'nutrient kicker', so using a slightly lower dose of nutrients untill you are used to the stuff, is recommended.

Usually, slight leaftip burn shows when you are reaching the upper limit of nutrients. (slight nutrient burn)

Does the soil the problem child is in dry quicker or slower than the others?
Is it directly in front of the fan, or in a corner of the growspace? Pictures of the problem child would help.