Justice is a fan-made global mod.

As far as I understand, djinns by their nature are not related to elemental magic, but to primordial magic, i.e., immunity to air is not justified for a djinn, but 50(75)% resistance to magic is quite acceptable. Regarding titans - yes, they do control lightning, but does that mean they should have immunity to it? They are not elementals, but mechanisms; it's one thing if we try to extinguish fire with fire (futilely casting a fireball at a fire elemental), and another thing if we throw a projectile at a cannon that shoots these projectiles itself.