It could be potassium deficiency. Symptoms include yellowing of leaf margins in the begining which later spread towards the veins. But the characteristic symptoms are marginal scorching (bronzing) and appearance of necrotic (chlorotic brown) spots in between the veins. Apply recommended quantities of wood ash or muriate of potash to overcome the problem.

Usually ants are associated with sucking insects like aphids, whiteflies, scale insects etc., So check your plants for any insect infestation.