With the launch of K.O. Coliseum, TFT is revising and evolving unit roles to offer more melee carries, weird but fun specialized units with different types of ultimates and attacks, and an overall more interesting gameplay experience. The game is changing how units gain mana depending on their roles, and how champions interact with different gameplay systems. For example, Tanks will now gain 5 mana per attack and will generate mana from taking damage. They'll also be at the center of aggression more often, making them more likely to be targeted. Meanwhile, casters will no longer generate mana from taking damage and will gain less mana per attack, but they’ll benefit from a small passive mana‐generation rate. The item system has also been overhauled so that most items now grant ongoing mana generation in place of initial mana.

These adjustments won't change how you've been playing TFT, but they will solve for edge cases like splash damage granting the enemy carries extra mana.