m0useanswered grow question 3 years ago The damaged growth will not repair its self.
Will need to pluck that off and monitor the other leaves to confirm its fixed/corrected.
As for how much CaMg you need, monitor your EC and keep it inline with what the plants are comfortable with. It will take up close to 1/2-1/3 your EC allowance. Will only need a heavy feeding at beginning to correct the issue then can tapper off into standard/lower ranges of concentration, some bottles have directions for how much, I find it's still best to use EC and go from there as they all suggest over feeding so you use more and then buy more.
Good Luck!