Leaf problem

Deficiencies in older leaves are signs of mobile nutrient shortages, such as Nitrogen and Phosphorous. Non mobile nutrient deficiencies show up in new growth. Looks like phosphorous deficiency, which does NOT necessarily mean that you don't have enough P. It can mean your pH is off and the plant isn't able to uptake it (so it takes the nutes from old leaves to provide P for new leaves, because P is a mobile nutrient). And pH issues can be caused by overfeeding. Flushing out salts from salt-based fertilizers (anything that comes in a bottle is dissolved solids) can help. And check the pH of runoff water and add acid or base to lower or raise pH. If you don't have pH up, you can use baking soda in water. If you don't have pH down you can use lemon juice.

First signs of burning from feeding too much/too often/too strong.