Magnesium Deficiency?

Shes a big plant in a small pot. Id suggest uppotting that to an 18L or around that. The edges are really mag related. Is stress from roots stranging each other and to much water intake. With big plants and small pots. There can be uptake off to much in such a small area if that makes sense. But, if never hurts to add a 250ppm Epsom salt feed to any plant especially in that stage. It'll the best source of mag/sulphur there is. But I don't think its that you need a bigger pot. The roots in that are such that small area so quickly its causing imbalances. . Good