Stonerdanswered grow question 4 years ago Hard to say from this picture, if its possible, provide a full picture of the plant showing where the deficiency is, the plants' diet, pH, and climate then it'll be less than a guess.
For now I'd say it's a Calcium (Ca) and Magnesium (Mg) deficiencies, and the best fix is to increase micro-nutrient fertilizer/Cal-Mag additive by 20% and monitor the damaged leaves for any improvement.
Hope this helps! Good luck and happy growing :)